New tire size help with tramlining
#41
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Good thinking. Not many people consider rim width versus tire size and many tire manufacturers often show as 'acceptable' rim widths that seem way too narrow for the tire, IMHO.
But I just peeked into the garage at my XJR wheels/tires (they're residing on a Ser III right now) and the 255/45s don't have the *appearance* of being too wide for the wheel....no 'pinched in' look at all, FWIW.
An extra 1/2" would probably be better for proper sidewall function/support but in this particular case I think it comes down to tire design/tread design more than rim width vs tire width. That is, 8.0" versus 8.5" probably isn't a major contributing factor in the notorious tramlining problem. IMHO of course.
Cheers
DD
But I just peeked into the garage at my XJR wheels/tires (they're residing on a Ser III right now) and the 255/45s don't have the *appearance* of being too wide for the wheel....no 'pinched in' look at all, FWIW.
An extra 1/2" would probably be better for proper sidewall function/support but in this particular case I think it comes down to tire design/tread design more than rim width vs tire width. That is, 8.0" versus 8.5" probably isn't a major contributing factor in the notorious tramlining problem. IMHO of course.
Cheers
DD
#42
If they made a 245/50-17, well they do, so.....
I changed my tyres to 235/50/17 Kuhmo,s
Because of the tram-lining issues I also have a set of anti tram-lining upper control arm bushes fitted that where designed by a fellow XJR owner when I was on the XJR6 forum
The anti tram-lining bushes did improve the tram-lining problem a bit with the 255/45/17 Falken ziex tyres but when they wore out I had my rims spun up trued and restored fitting the 235/50/17 Kuhmo,s
I would never go back to the 255/45/17 tyres again even if someone gave me a brand new set of Michelin,s
I would put them on-line and sell them
The 255/45/17 tyres are okay if you are racing but round town and everyday use the 235/50/17 are a superior choice
1 The car is smoother and less rough riding more like a jaguar should be even though I run 40 psi in them
2 The car handles better with the smaller tyres
Before the car would dig in and under-steer badly pretty frightening when you are heading for a wall now with the 235/5017,s I can induce over-steer easily with my right foot
3 As the side wall is slightly higher no gutter rash on my rims after 3 years
4 they have a much straighter side-wall less tyre rolling around and look really good on the 8 inch rims
I get more comments on the 235/50/17,s then I did on the 255/45/17,s don't ask me why I just do
My speedo was 6 k,s out with the 255/45/17,s it now 4 k,s out I think if they made 245/50/17,s the speedo would be close to spot on
5 I am really happy with the Kuhmo,s reasonably priced last long and grip well even in tropical down pours that are a regular occurrence here in summer I cant vouch for them in cold climates doesn't get under double digits here even in the middle of winter at 4 in the morning
Hope this helps there are quite a few brands of 235/50/17 tyres on the market do some research and look for some feed back not necessarily on the tyre size you are looking at but the tyre model
Tire-rack lead me in the right direction a couple of times with their tyre feedback,s
And as you can see in the photo,s they don't look wrong on the car
Because of the tram-lining issues I also have a set of anti tram-lining upper control arm bushes fitted that where designed by a fellow XJR owner when I was on the XJR6 forum
The anti tram-lining bushes did improve the tram-lining problem a bit with the 255/45/17 Falken ziex tyres but when they wore out I had my rims spun up trued and restored fitting the 235/50/17 Kuhmo,s
I would never go back to the 255/45/17 tyres again even if someone gave me a brand new set of Michelin,s
I would put them on-line and sell them
The 255/45/17 tyres are okay if you are racing but round town and everyday use the 235/50/17 are a superior choice
1 The car is smoother and less rough riding more like a jaguar should be even though I run 40 psi in them
2 The car handles better with the smaller tyres
Before the car would dig in and under-steer badly pretty frightening when you are heading for a wall now with the 235/5017,s I can induce over-steer easily with my right foot
3 As the side wall is slightly higher no gutter rash on my rims after 3 years
4 they have a much straighter side-wall less tyre rolling around and look really good on the 8 inch rims
I get more comments on the 235/50/17,s then I did on the 255/45/17,s don't ask me why I just do
My speedo was 6 k,s out with the 255/45/17,s it now 4 k,s out I think if they made 245/50/17,s the speedo would be close to spot on
5 I am really happy with the Kuhmo,s reasonably priced last long and grip well even in tropical down pours that are a regular occurrence here in summer I cant vouch for them in cold climates doesn't get under double digits here even in the middle of winter at 4 in the morning
Hope this helps there are quite a few brands of 235/50/17 tyres on the market do some research and look for some feed back not necessarily on the tyre size you are looking at but the tyre model
Tire-rack lead me in the right direction a couple of times with their tyre feedback,s
And as you can see in the photo,s they don't look wrong on the car
XJR stock tire comparison.
255/45R17 Imperial Metric Section Width: 10.04 in 255.00 mm Rim Diameter: 17 in 431.8 mm Rim Width Range: 8 - 9.5 in Overall Diameter: 26.04 in 661.30 mm Sidewall Height: 4.52 in 114.75 mm Radius: 13.02 in 330.65 mm Circumference: 81.79 in 2,077.54 mm Revs per Mile: 798.91/mi Actual Speed: 62.14 mph 100.00 kph Speed Variance: - Diameter Variance: -
Tire Size 1 235/50R17 Imperial Metric Section Width: 9.25 in 235.00 mm Rim Diameter: 17 in 431.8 mm Rim Width Range: 6.5 - 8.5 in Overall Diameter: 26.25 in 666.80 mm Sidewall Height: 4.63 in 117.50 mm Radius: 13.13 in 333.40 mm Circumference: 82.47 in 2,094.81 mm Revs per Mile: 792.32/mi Actual Speed: 62.65 mph 100.83 kph Speed Variance: 0.82% too fast. Diameter Variance: 0.83%
Tire Size 2 245/50R17 Imperial Metric Section Width: 9.65 in 245.00 mm Rim Diameter: 17 in 431.8 mm Rim Width Range: 7 - 8.5 in Overall Diameter: 26.65 in 676.80 mm Sidewall Height: 4.82 in 122.50 mm Radius: 13.32 in 338.40 mm Circumference: 83.71 in 2,126.23 mm Revs per Mile: 780.61/mi Actual Speed: 63.59 mph 102.34 kph Speed Variance: 2.29% too fast. Diameter Variance: 2.34%
XJ6 stock tire comparison
Section Width: 8.86 in 225.00 mm Rim Diameter: 16 in 406.4 mm Rim Width Range: 6 - 9 in Overall Diameter: 26.63 in 676.40 mm Sidewall Height: 5.31 in 135.00 mm Radius: 13.31 in 338.20 mm Circumference: 83.66 in 2,124.97 mm Revs per Mile: 781.08/mi Actual Speed: 62.14 mph 100.00 kph Speed Variance: - Diameter Variance: -
Tire Size 1 235/50R17 Imperial Metric Section Width: 9.25 in 235.00 mm Rim Diameter: 17 in 431.8 mm Rim Width Range: 6.5 - 8.5 in Overall Diameter: 26.25 in 666.80 mm Sidewall Height: 4.63 in 117.50 mm Radius: 13.13 in 333.40 mm Circumference: 82.47 in 2,094.81 mm Revs per Mile: 792.32/mi Actual Speed: 61.26 mph 98.58 kph Speed Variance: 1.44% too slow. Diameter Variance: -1.42%
Tire Size 2 245/50R17 Imperial Metric Section Width: 9.65 in 245.00 mm Rim Diameter: 17 in 431.8 mm Rim Width Range: 7 - 8.5 in Overall Diameter: 26.65 in 676.80 mm Sidewall Height: 4.82 in 122.50 mm Radius: 13.32 in 338.40 mm Circumference: 83.71 in 2,126.23 mm Revs per Mile: 780.61/mi Actual Speed: 62.17 mph 100.06 kph Speed Variance: 0.06% too fast. Diameter Variance: 0.06%
Summary
Compared to OEM XJR 255/45-17 tire:
235/50-17 .82% too fast
245/50-17 2.29% too fast
Compared to OEM XJ6 225/60-16 tire:
235/50-17 1.44% too slow
245/50-17 .06% too fast
And then comparing the 225/60-16 XJ6 tires with the 255/45-17 XJR tires, we find that the XJR tires are interestingly 2.23% too slow.
So here's a question probably no one knows.... is the XJR speedo calibrated to account for the XJR tires being 2.23% slower than a regular XJ6 tire? If not and the XJR and XJ6 speedos are calibrated the same, then indeed it looks like the 245/50-17 is indeed an almost perfect "+1" match to the XJ6 tire, at least in indicated speed and diameter. So if the XJR speedo is really off by 2.28%, this 245 tire would get it back to spot on accuracy.
Bottom line the 225/60-16 and 245/70-17 tires only have a .4mm difference in overall diameter. That's darned close.
And the load ratings for the 245/50-17 tires seem to be readily available in the appropriate 98+ load ratings, where the 235/50-17 seem mostly/all to be 96 load rated.
So I wonder if the 245/50-17 may actually be the ideal fit and if they would be narrower and/or taller enough to have the same positive effect reducing tramlining as the 235/50-17 has been reported to produce?
.
Last edited by al_roethlisberger; 06-11-2014 at 10:18 PM.
#43
#44
Some other owner's thoughts on 255 tires being too wide for the OEM wheels.
Good thinking. Not many people consider rim width versus tire size and many tire manufacturers often show as 'acceptable' rim widths that seem way too narrow for the tire, IMHO.
But I just peeked into the garage at my XJR wheels/tires (they're residing on a Ser III right now) and the 255/45s don't have the *appearance* of being too wide for the wheel....no 'pinched in' look at all, FWIW.
An extra 1/2" would probably be better for proper sidewall function/support but in this particular case I think it comes down to tire design/tread design more than rim width vs tire width. That is, 8.0" versus 8.5" probably isn't a major contributing factor in the notorious tramlining problem. IMHO of course.
Cheers
DD
But I just peeked into the garage at my XJR wheels/tires (they're residing on a Ser III right now) and the 255/45s don't have the *appearance* of being too wide for the wheel....no 'pinched in' look at all, FWIW.
An extra 1/2" would probably be better for proper sidewall function/support but in this particular case I think it comes down to tire design/tread design more than rim width vs tire width. That is, 8.0" versus 8.5" probably isn't a major contributing factor in the notorious tramlining problem. IMHO of course.
Cheers
DD
Here's an interesting thread in the X308 section talking a bit about the subject of Jaguar choosing 255 tires for an 8" wide rim:
https://www.jaguarforums.com/forum/x...g-tires-70678/
1999XJR
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My Thesis on XJR Drag Tires
I would like to take my XJR to the occasional day at the drag strip.
With that in mind, I have been looking at D.O.T. approved drag tires.
My XJR came stock with 18" x 8" wheels, and 255/40 R18 tires.
First off, let's talk tire widths. Most 255 wide tires have a recommended wheel width of 8.5" - 10". For some reason Jaguar decided to mount these tires on extra-skinny wheels of 8" width. Strange. For 8" wide wheels, they would typically recommend either 235 or 245 wide tires. Anyone have any insight as to why they would do this?
Also, mounting a tire on an extra-skinny wheel will decrease the section width of the tire. A 255/R18 tire is usually measured on a 9" wide wheel. Every 0.5" you reduce the wheel width by, you reduce the section width by about 2/10". This means that if a 255 tire is 10.04" wide (255mm / 25.4) when mounted on a 9" wheel, it will only be 9.64" (245mm) when mounted on an 8" wheel.
So instead of mounting a 245mm tire on an 8.5" wheel, they increased the tire to 255mm and mounted it on an extra-skinny 8" wheel.
This might have something to do with load rating. Jaguar recommends the Pirelli P-Zero tire for the 18" wheels. These have a rating of 99Y. The 99 means each tire can handle 1,709 lbs while the Y means 186mph. This is a rediculously high load rating for such a high-speed tire. This probably has to do with the fact that this car weighs 4,200 lbs WITHOUT PASSENGERS!
Let's say I wanted to go the "normal" route, and mount 245/R18 tires on an 8.5" wheel. I would still want a 99Y tire. I could go with either a 245/40R18 (25.72" diameter) or a 245/45R18 (26.68" diameter) tire.
In the 245/40 category, assuming I want to maintain the Y speed rating, the highest load rating I could find was a few tires with a 97 rating (1,609 lbs), with most being 93 rating (1,433 lbs) or lower.
In the 245/45 category, assuming I want to maintain the Y speed rating, there are several with a load rating of 100 (1,764 lbs). Perhaps this option didn't give the "low-profile" look Jaguar was after (4.34" sidewall vs. 4.01" sidewall) ?
Secondly, let's look at diameter. The the stock tire was approximately 26.03" in diameter. With passenger tires, it's best to stay within 3% of the stock diameter. This means going no larger than 26.81" in diameter.
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My Thesis on XJR Drag Tires
I would like to take my XJR to the occasional day at the drag strip.
With that in mind, I have been looking at D.O.T. approved drag tires.
My XJR came stock with 18" x 8" wheels, and 255/40 R18 tires.
First off, let's talk tire widths. Most 255 wide tires have a recommended wheel width of 8.5" - 10". For some reason Jaguar decided to mount these tires on extra-skinny wheels of 8" width. Strange. For 8" wide wheels, they would typically recommend either 235 or 245 wide tires. Anyone have any insight as to why they would do this?
Also, mounting a tire on an extra-skinny wheel will decrease the section width of the tire. A 255/R18 tire is usually measured on a 9" wide wheel. Every 0.5" you reduce the wheel width by, you reduce the section width by about 2/10". This means that if a 255 tire is 10.04" wide (255mm / 25.4) when mounted on a 9" wheel, it will only be 9.64" (245mm) when mounted on an 8" wheel.
So instead of mounting a 245mm tire on an 8.5" wheel, they increased the tire to 255mm and mounted it on an extra-skinny 8" wheel.
This might have something to do with load rating. Jaguar recommends the Pirelli P-Zero tire for the 18" wheels. These have a rating of 99Y. The 99 means each tire can handle 1,709 lbs while the Y means 186mph. This is a rediculously high load rating for such a high-speed tire. This probably has to do with the fact that this car weighs 4,200 lbs WITHOUT PASSENGERS!
Let's say I wanted to go the "normal" route, and mount 245/R18 tires on an 8.5" wheel. I would still want a 99Y tire. I could go with either a 245/40R18 (25.72" diameter) or a 245/45R18 (26.68" diameter) tire.
In the 245/40 category, assuming I want to maintain the Y speed rating, the highest load rating I could find was a few tires with a 97 rating (1,609 lbs), with most being 93 rating (1,433 lbs) or lower.
In the 245/45 category, assuming I want to maintain the Y speed rating, there are several with a load rating of 100 (1,764 lbs). Perhaps this option didn't give the "low-profile" look Jaguar was after (4.34" sidewall vs. 4.01" sidewall) ?
Secondly, let's look at diameter. The the stock tire was approximately 26.03" in diameter. With passenger tires, it's best to stay within 3% of the stock diameter. This means going no larger than 26.81" in diameter.
I particularly found the following interesting:
This means that if a 255 tire is 10.04" wide (255mm / 25.4) when mounted on a 9" wheel, it will only be 9.64" (245mm) when mounted on an 8" wheel.
Seems like that gives even more creedance to a 235 or 245 tire being a more appropriate fit. That has to help with wear and possibly ride?
And again, while I've found no 235 tires (via a cursory, but not extensive search) that meet the 98/99 load rating of the OEM tires, I have found several 245 tires that do.
So maybe 245 is worth a test to see if it is a size as good at minimizing tramlining as the 235 tires have been shown to be?
It would be fantastic to hear if anyone has tried 245s and evaluated their impact on tramlining and general ride quality and performance.
.
Last edited by al_roethlisberger; 06-12-2014 at 02:12 PM.
#45
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I've not tried the 245s (or 235s) so I can't comment.
Besides tire size I think it would interesting to examine/research tread pattern and shoulder design and see where that fits into the tramlining issue.
We already know from years of commenting that different 255s behave differently, including significantly different degrees of tramlining. So size is only one factor, albeit it seems to be an important one as we know that if you make a significant enough reduction in width (and an increase in aspect ratio) you're virtually assured of eliminating tramlining.
As an aside (referring to the above quoted commentary) I get a bit of a kick about regarding 8.5" as a good rim width for 255s but calling 8.0" rim width 'extra-skinny'
Cheers
DD
Besides tire size I think it would interesting to examine/research tread pattern and shoulder design and see where that fits into the tramlining issue.
We already know from years of commenting that different 255s behave differently, including significantly different degrees of tramlining. So size is only one factor, albeit it seems to be an important one as we know that if you make a significant enough reduction in width (and an increase in aspect ratio) you're virtually assured of eliminating tramlining.
As an aside (referring to the above quoted commentary) I get a bit of a kick about regarding 8.5" as a good rim width for 255s but calling 8.0" rim width 'extra-skinny'
Cheers
DD
#46
Tire FAQ?
I've not tried the 245s (or 235s) so I can't comment.
Besides tire size I think it would interesting to examine/research tread pattern and shoulder design and see where that fits into the tramlining issue.
We already know from years of commenting that different 255s behave differently, including significantly different degrees of tramlining. So size is only one factor, albeit it seems to be an important one as we know that if you make a significant enough reduction in width (and an increase in aspect ratio) you're virtually assured of eliminating tramlining.
As an aside (referring to the above quoted commentary) I get a bit of a kick about regarding 8.5" as a good rim width for 255s but calling 8.0" rim width 'extra-skinny'
Cheers
DD
Besides tire size I think it would interesting to examine/research tread pattern and shoulder design and see where that fits into the tramlining issue.
We already know from years of commenting that different 255s behave differently, including significantly different degrees of tramlining. So size is only one factor, albeit it seems to be an important one as we know that if you make a significant enough reduction in width (and an increase in aspect ratio) you're virtually assured of eliminating tramlining.
As an aside (referring to the above quoted commentary) I get a bit of a kick about regarding 8.5" as a good rim width for 255s but calling 8.0" rim width 'extra-skinny'
Cheers
DD
Maybe we should start to solicit that feedback, compile it and then just make a list, much like the list for compatible OBD readers?
.
#47
#48
..... and see posts #21 and #23 in the following 'differential' thread:
https://www.jaguarforums.com/forum/x...e2/#post640068
Doc mentions he played with tire sizes on his XJR to get his speedo accurate to coincide with the speed cameras. What tire size worked out to make the speedo accurate?
245/50-17
https://www.jaguarforums.com/forum/x...e2/#post640068
Doc mentions he played with tire sizes on his XJR to get his speedo accurate to coincide with the speed cameras. What tire size worked out to make the speedo accurate?
245/50-17
#50
Hi Doc, a little confused by your question above as your post linked below seemed to suggest you installed 245/50-17 tires to get the speedo spot on accurate:
https://www.jaguarforums.com/forum/x...e2/#post640068
Hi Plums I have 245/50/17 tyres on my car makes the speedo exact and since fitting the 3.58 diff I have seen higher top speeds consistently than with the 3.27 the car now gets there instead of wasting time trying to get there
My speedo was always out by 8 k,s the diff gears made no difference because the speedo is driven by one of the rear wheel sensors so your speedo shouldn't need recalibrating I played with tyres to get the speedo exact for the speed cameras (LOL)
But, here in the US there are a lot of 245/50-17 tires to choose from that are appropriate load rating and speed rating. I shopped at tirerack.com and found quite a few mainstream brands.
http://www.tirerack.com/tires/TireSe...50&diameter=17
Hope that helps answer your question about general availability.
.
#51
Yeah must have Got that one wrong somewhere
Got 235/50/17,s on it
I did see the 245/50/17,on Tirerack thought I might try ordering a set to deliver them to Australia next time seems Tirerack do ship to Australia
But don't think I,ll be needing them soon the XJR6 is in the garage with trickle charger under a cover up for sale haven't driven it in 3 months
Just got my XJ8 X350 sorted last Friday for it only to break the nipple of the header tank Saturday morning on the way to get it washed and refuelled for a trip to Brisbane
oh well got to watch plenty of TV shows recorded and none of them by the wife LOL
Got 235/50/17,s on it
I did see the 245/50/17,on Tirerack thought I might try ordering a set to deliver them to Australia next time seems Tirerack do ship to Australia
But don't think I,ll be needing them soon the XJR6 is in the garage with trickle charger under a cover up for sale haven't driven it in 3 months
Just got my XJ8 X350 sorted last Friday for it only to break the nipple of the header tank Saturday morning on the way to get it washed and refuelled for a trip to Brisbane
oh well got to watch plenty of TV shows recorded and none of them by the wife LOL
#52
#53
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I might've mentioned that I've been running 225/60x16 tires on my XJR for many years now. However, encouraged by so many happy results using size 235/50x17 I decided to jump on the bandwagon myself.
I bought "Sumitomo HTR Enhance". These have a V-speed rating, 600 treadlife rating, and A-A traction-Temp rating.
The load rating of '96' is a bit lower than I'd prefer but obviously not to the extent that I feel unsafe using them
So far I happy report: no tramlining, slightly nosier than the previous BFG Advantage tires but certainly not excessively so. The ride is a tad firmer and the steering a bit sharper....to be generally expected, I reckon, when going from a 60-series to a 50-series.
In my neck o' the woods wet traction is very important. I'll be able to report on that in a few weeks.
Only $100 each before $50 mail in rebate.
No complaints
Cheers
DD
PS- I forgot a very pleasant bonus. The last bits of vibration are finally gone! I think one of the old tires had gone a wee bit lumpy with accumulation of age and miles.
I bought "Sumitomo HTR Enhance". These have a V-speed rating, 600 treadlife rating, and A-A traction-Temp rating.
The load rating of '96' is a bit lower than I'd prefer but obviously not to the extent that I feel unsafe using them
So far I happy report: no tramlining, slightly nosier than the previous BFG Advantage tires but certainly not excessively so. The ride is a tad firmer and the steering a bit sharper....to be generally expected, I reckon, when going from a 60-series to a 50-series.
In my neck o' the woods wet traction is very important. I'll be able to report on that in a few weeks.
Only $100 each before $50 mail in rebate.
No complaints
Cheers
DD
PS- I forgot a very pleasant bonus. The last bits of vibration are finally gone! I think one of the old tires had gone a wee bit lumpy with accumulation of age and miles.
#54
I might've mentioned that I've been running 225/60x16 tires on my XJR for many years now. However, encouraged by so many happy results using size 235/50x17 I decided to jump on the bandwagon myself.
I bought "Sumitomo HTR Enhance". These have a V-speed rating, 600 treadlife rating, and A-A traction-Temp rating.
The load rating of '96' is a bit lower than I'd prefer but obviously not to the extent that I feel unsafe using them
So far I happy report: no tramlining, slightly nosier than the previous BFG Advantage tires but certainly not excessively so. The ride is a tad firmer and the steering a bit sharper....to be generally expected, I reckon, when going from a 60-series to a 50-series.
In my neck o' the woods wet traction is very important. I'll be able to report on that in a few weeks.
Only $100 each before $50 mail in rebate.
No complaints
Cheers
DD
PS- I forgot a very pleasant bonus. The last bits of vibration are finally gone! I think one of the old tires had gone a wee bit lumpy with accumulation of age and miles.
I bought "Sumitomo HTR Enhance". These have a V-speed rating, 600 treadlife rating, and A-A traction-Temp rating.
The load rating of '96' is a bit lower than I'd prefer but obviously not to the extent that I feel unsafe using them
So far I happy report: no tramlining, slightly nosier than the previous BFG Advantage tires but certainly not excessively so. The ride is a tad firmer and the steering a bit sharper....to be generally expected, I reckon, when going from a 60-series to a 50-series.
In my neck o' the woods wet traction is very important. I'll be able to report on that in a few weeks.
Only $100 each before $50 mail in rebate.
No complaints
Cheers
DD
PS- I forgot a very pleasant bonus. The last bits of vibration are finally gone! I think one of the old tires had gone a wee bit lumpy with accumulation of age and miles.
Did you mean 235/50x17 or 245/50x17?
Heh, nevermind, went and looked at the specs. Looks like the 235 is what was available and is a good size match.
.
Last edited by al_roethlisberger; 09-14-2014 at 11:55 AM.
#55
Anyone have any experience with the new Pirelli P7 Centurato?
I started a thread in the "Tires & Wheels" section, but no one has replied.
https://www.jaguarforums.com/forum/w...rience-126266/
.
I started a thread in the "Tires & Wheels" section, but no one has replied.
https://www.jaguarforums.com/forum/w...rience-126266/
.
#56
I know it's not the same chassis, but I'm running 235/50-18s on my VDP. That is the stock tire size, but I've got them on 8.5 wide wheels, which is the maximum width wheel recommended for 235s. I made the mistake of putting 245s that run wider than most on the 8 in wide wheels on my GTO and it felt sloppy in hard turns compared to the 235s the stock wheels came with. I only went with 245s because the place I bought tires from because they couldn't source the 235s at the time that I wanted. They looked ballooned to me on the 8 inch wheel and that was a 40 series tire on that car.
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al_roethlisberger (09-18-2014)
#57
I'm thinking about going with either the 245/50-17 or 245/45-17.
In looking through the 235/50-17 options, none except one Hankook tire meet the load spec for the XJR. Most in this size are 95-96 load ratings, where the XJR requires 98-99.
But the 245/45 and 245/50 sizes do come in the correct load rating. The 245/45 also has a lot more choices, especially for higher mileage tires like the Continental Purecontact and Michelin Sport A/S
The 245/45 is very close in size, but just a little bit smaller in diameter/circumference, losing about 5mm in sidewall height.
One can see the difference here:
255/45-R17 vs 245/45-R17 Tire Comparison - Tire Size Calculator
The 245/50 is the next runner-up but is a bit bigger, being about 8mm taller.
255/45-R17 vs 245/50-R17 Tire Comparison - Tire Size Calculator
Any thoughts on issues or preference with either choice in size.
I could also stick with the OEM size of 255/45-17 as I've gotten fairly used to the tramlining now to tell you the truth.... but all of the tires in this size have very poor mileage, and I need something with 50k or more treadlife given how many miles I drive.
.
In looking through the 235/50-17 options, none except one Hankook tire meet the load spec for the XJR. Most in this size are 95-96 load ratings, where the XJR requires 98-99.
But the 245/45 and 245/50 sizes do come in the correct load rating. The 245/45 also has a lot more choices, especially for higher mileage tires like the Continental Purecontact and Michelin Sport A/S
The 245/45 is very close in size, but just a little bit smaller in diameter/circumference, losing about 5mm in sidewall height.
One can see the difference here:
255/45-R17 vs 245/45-R17 Tire Comparison - Tire Size Calculator
The 245/50 is the next runner-up but is a bit bigger, being about 8mm taller.
255/45-R17 vs 245/50-R17 Tire Comparison - Tire Size Calculator
Any thoughts on issues or preference with either choice in size.
I could also stick with the OEM size of 255/45-17 as I've gotten fairly used to the tramlining now to tell you the truth.... but all of the tires in this size have very poor mileage, and I need something with 50k or more treadlife given how many miles I drive.
.
#58
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I faced the same quandry. I'm not sure it quite correct to say that the car 'requires' 98 or 99 load rating. Jaguar elected to use a 98 or 99 load rating tire. Obviously, though, you want a tire that'll support the weight of the car and then some.
The XJR/6 has a curb weight of 4200 pounds and a max allowable gross weight of (something like) 5000 pounds. That is, five passengers + luggage = about 5000 pounds max.
'96' load rating = 1565 pounds x 4 = 6260 pounds
'98' load rating = 1653 pounds x 4 = 6612 pounds
So, you gain 352 pounds of additional margin.
Since I drive alone 99.99% of the time (I don't think the back seat has been used six times in as many years) I decided the '96' tires wouldn't pose any unreasonable risk.
An owner driver who drives with under-inflates tires, due to simple laziness or neglect, is more likely to need that extra 352 pound margin. I'm quite sure you keep on top of such things, though !
In the end I'd say it's a valid concern but I wouldn't let load rating alone disqualify a tire that you're otherwise happy to consider. I didn't
Just my two cents.
Cheers
DD
PS- one word about the tire size calculators:
These are a real boon BUT do double check tire specs from the manufacturer. The standards here seem to be a bit low. For any given size designation you can sometimes find manufacturer-to-manufacturer differences in actual, final dimensions. I've seen as much as 5% in some cases.
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al_roethlisberger (09-19-2014)
#59
Maybe 245/50-17 really is the 'secret' OEM size for the XJR?
Thanks Doug
Question though, if you (or anyone else) had to choose between the slightly 'shorter' 245/45 or more than slightly 'taller' 245/50 tire on the XJR, where would you lean and why?
I have my thoughts to some degree, but am curious what others may consider that I haven't.
As an interesting aside, for what it's worth.... the 1997 XK8, also fitted with 17x8 rims, has 245/50-17 size as the OEM size.
As another interesting thought/question: Does anyone know if the XJR speedo with the OEM 255/45-17 tires is accurate, or is actually a bit 'off' and still calibrated to the non-XJR XJ6 225/60-16 tire/rim size?
Because, it appears that the closest match (NEARLY IDENTICAL) in diameter/circumference is between the XJ6 225/60-16 and XK8 245/50-17:
http://www.tacomaworld.com/forum/tir...0r16-245-50r17
*If* the XJR speedo is still really calibrated against a regular XJ6 225/60-16 tire size (versus the XJR 255/45-17), *and* the XK8 17x8 rim is spec'd for a 245/50-17 which is apparently almost exactly the same diameter/cirucmference as the XJ6 225/60-16 tire.... PHEW
.... well then that may argue that the ideal tire size on the XJR really is 245/50-17
Much appreciated
.
Question though, if you (or anyone else) had to choose between the slightly 'shorter' 245/45 or more than slightly 'taller' 245/50 tire on the XJR, where would you lean and why?
I have my thoughts to some degree, but am curious what others may consider that I haven't.
As an interesting aside, for what it's worth.... the 1997 XK8, also fitted with 17x8 rims, has 245/50-17 size as the OEM size.
As another interesting thought/question: Does anyone know if the XJR speedo with the OEM 255/45-17 tires is accurate, or is actually a bit 'off' and still calibrated to the non-XJR XJ6 225/60-16 tire/rim size?
Because, it appears that the closest match (NEARLY IDENTICAL) in diameter/circumference is between the XJ6 225/60-16 and XK8 245/50-17:
http://www.tacomaworld.com/forum/tir...0r16-245-50r17
*If* the XJR speedo is still really calibrated against a regular XJ6 225/60-16 tire size (versus the XJR 255/45-17), *and* the XK8 17x8 rim is spec'd for a 245/50-17 which is apparently almost exactly the same diameter/cirucmference as the XJ6 225/60-16 tire.... PHEW
.... well then that may argue that the ideal tire size on the XJR really is 245/50-17
Much appreciated
.
Last edited by al_roethlisberger; 09-19-2014 at 12:17 PM.
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All else being equal I'd go with a bit taller. Why? I favor a taller sidewall. My personal experience (on various cars, including Jags, and including the XJR) with 40 and 45 series tires has been rather poor. My personal experience with 50-55-60 series tires has been generally good.
You'd think the difference between 45 series and 50 series wouldn't amount to a hill a beans but it seems to be an important 5%.
Back when I was running the 255/45 tires one of my big complaints was road damage. I had to replace several tires and have a couple wheels repaired, over a period of 3-4 years. I've never had that happen with 50-or higher series tires. Pure coincidence? I dunno. Obviously there are variables but maybe, for a 4200 pound car, the difference between 45 and 50 just sorta puts things over the edge?
(Aside: I don't know how the guys running those 25-30-35 series tires tolerate all the road damage problems. You can read about here and on other car forums. It's quite common)
As far as the actual driving performance of the tire goes I doubt the 45 vs. 50 difference, in and of itself, would make much difference. Any difference you feel might well come down to the design of the tire (tread, casing, compound, etc) as much or more than the 5% difference in aspect ratio
Cheers
DD
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al_roethlisberger (09-19-2014)