Help! starting this project

[XLRJIM]

Almost bought a salvage XLR

I must have lost my mind but not my enthusiasm LOL

I almost bought an 05 that was totaled by the insurance company, Front end wiped out broken windshield, tons of other damage. My wife said I don't know and my bodyshop friend said no way. Still I admire you guys that have or are rebuilding one. What a project! Good luck and congratulations. JIM

 

[rockyrhoads]

tires

okay getting ready to buy tires. what can I go to size wise for maximum width on stock 19 inch wheels. Rocky

 

[Phrede]

okay getting ready to buy tires. what can I go to size wise for maximum width on stock 19 inch wheels. Rocky

Big point of discussion here.

I will not say what the biggest is. I will say that I run 255/40-19 on stock rims all 4 corners. No problems.

IMHO, get better performance by tire model/compound. Size is not everything.

 

[rockyrhoads]

compound is not the issue

Big point of discussion here.

I will not say what the biggest is. I will say that I run 255/40-19 on stock rims all 4 corners. No problems.

IMHO, get better performance by tire model/compound. Size is not everything.

I understand all about compound as I have raced stock cars for many years. I will get to the compound later just wondered if any one knew what the max size IE 265/30-19 rear would be overextended for the stock rims. The stagger that is engineered into the cars geometry of the front suspension is very important to performance by the way Rocky

 

[Phrede]

I understand all about compound as I have raced stock cars for many years. I will get to the compound later just wondered if any one knew what the max size IE 265/30-19 rear would be overextended for the stock rims. The stagger that is engineered into the cars geometry of the front suspension is very important to performance by the way Rocky

Since our cars use the same wheel front and rear and the center of the contact patch is exactly the same as is the tire OD, IMHO changing the front tire width by 20mm to match the rear has very little, if any effect on steering geometry or handling performance.

 

[rockyrhoads]

geometry

Since our cars use the same wheel front and rear and the center of the contact patch is exactly the same as is the tire OD, IMHO changing the front tire width by 20mm to match the rear has very little, if any effect on steering geometry or handling performance.

okay maybe a little talk about performance and tires. The wheel size may be the same from the factory but the tire size is different. This difference not only drops the nose into the wind but reduces the total tire weight. This brings to the equation a term called rotating weight which multiplies the gyro forces that are in play. If you increase the front tire size to match the rear you have raised the nose reducing down force an adding not only weight but rotating weight. More weight takes more horsepower to move, the rise of the nose takes away downforce reducing traction and steering and then there is rotating weight and gyro force which will cause the front end to push as rotating weight will want to move in a straight line so if we increase the front tire size the combination is a loss of power and control. So no matter if you are straight line racing or road course racing you have lost power and steering. By increasing the width without increasing height I can get a larger contact patch while still keeping my nose in the wind an minimizing the weight addition and rotating weight. It was a simple question and I can calculate the maximum width for the stock wheel just thought someone out there had the info. If you go too wide the rim will crown the tread and reduce the contact patch so the whole thing is redundant not to mention the stress that would be placed on the sidewall. Compound will give you more grip but less tread life and although grip is important the overall equation of geometry, caster, camber, toe and contact area will overcome any extra grip with less tire wear and as the icons always say" To finish first, First you must finish" The one that takes it all into play will drive by those that rely on only a few of the factors......IMHO.......Rocky

 

[Phrede]

okay maybe a little talk about performance and tires. The wheel size may be the same from the factory but the tire size is different. This difference not only drops the nose into the wind but reduces the total tire weight. This brings to the equation a term called rotating weight which multiplies the gyro forces that are in play. If you increase the front tire size to match the rear you have raised the nose reducing down force an adding not only weight but rotating weight. More weight takes more horsepower to move, the rise of the nose takes away downforce reducing traction and steering and then there is rotating weight and gyro force which will cause the front end to push as rotating weight will want to move in a straight line so if we increase the front tire size the combination is a loss of power and control. So no matter if you are straight line racing or road course racing you have lost power and steering. By increasing the width without increasing height I can get a larger contact patch while still keeping my nose in the wind an minimizing the weight addition and rotating weight. It was a simple question and I can calculate the maximum width for the stock wheel just thought someone out there had the info. If you go too wide the rim will crown the tread and reduce the contact patch so the whole thing is redundant not to mention the stress that would be placed on the sidewall. Compound will give you more grip but less tread life and although grip is important the overall equation of geometry, caster, camber, toe and contact area will overcome any extra grip with less tire wear and as the icons always say" To finish first, First you must finish" The one that takes it all into play will drive by those that rely on only a few of the factors......IMHO.......Rocky

The stock rear tires are actually shorter than the fronts by .296". So putting stock rear tire size on the front actually lowers the front by a whopping .148". I suppose this could effect the caster a very small amount, which is why all alignments should be checked. A good idea regardless of your choice of tires.

For performance gains, getting rid of the run flats would be first on my list. Being able to do a 4 tire rotation is a plus of a non-stagger configuration. I disagree with your comment that contact area can overcome any gains of using a smaller tire with a more performance oriented design.

I think this is going to be more of a discussion as it appears finding the stock tires of the stagger fit is no longer available. Both the Pierelli and Tire Rack websites claims they have nothing to fit an XLR-V.

 

[rockyrhoads]

Tires

The stock rear tires are actually shorter than the fronts by .296". So putting stock rear tire size on the front actually lowers the front by a whopping .148". I suppose this could effect the caster a very small amount, which is why all alignments should be checked. A good idea regardless of your choice of tires.

For performance gains, getting rid of the run flats would be first on my list. Being able to do a 4 tire rotation is a plus of a non-stagger configuration. I disagree with your comment that contact area can overcome any gains of using a smaller tire with a more performance oriented design.

I think this is going to be more of a discussion as it appears finding the stock tires of the stagger fit is no longer available. Both the Pierelli and Tire Rack websites claims they have nothing to fit an XLR-V.

Not trying to get into a contest of words. It seems that your time on the highway much surpasses my track time and many years of tire usage. Tire rack gave me the same Pirelli sizes as I have now but since they were on the car when purchased they may not be stock(235/45 front..255/40..rear) I asked a simple question and all I seem to get is info that does not answer the question. I will get in touch with my friends at goodyear. Your comment that a little does not seem to make much of a difference seems to differ with the fact that sometimes I changed tire pressures by a quarter pound to get the performance I needed and kept me from plowing to the wall but again what do I know. I will refrain from asking questions here

 

[Phrede]

Not trying to get into a contest of words. It seems that your time on the highway much surpasses my track time and many years of tire usage. Tire rack gave me the same Pirelli sizes as I have now but since they were on the car when purchased they may not be stock(235/45 front..255/40..rear) I asked a simple question and all I seem to get is info that does not answer the question. I will get in touch with my friends at goodyear. Your comment that a little does not seem to make much of a difference seems to differ with the fact that sometimes I changed tire pressures by a quarter pound to get the performance I needed and kept me from plowing to the wall but again what do I know. I will refrain from asking questions here

Not a contest of words, simply facts. Your comment that the stagger fit caused the front end to be lower is false. Just facts. It seems that when asking questions you would want accurate answers. Maybe not.

The Tire Rack website now claims that a set of run flat tires are not available in the OEM size, as does Pirelli which is what was on some Vs from the factory. Finding the OEM tire size is not that hard. It appears that finding OEM replacement tires is going to be harder.

You incorrectly quoted me as I never said that something little can not make a difference. What I said was that a better tire with a smaller contact patch could out perform a larger tire of a lesser design.

You have no idea what my knowledge or experience is maybe you should not make assumptions.

Sorry I responded. Good luck with your search.

 

[rockyrhoads]

goodyear answers

my friends at goodyear have given me my answer..245/35 front and 265/30 rear. I have 2 porsches and 2 late model stock cars with which I run hard on the track. This car will be on the street and the compound will be chosen for a mix of durability and traction in normal driving conditions. I will be sticking with the run flats as there is no room for a spare and since I have just spent 6K on body parts to rebuild this wonderful car I do not want to think about what would happen to it if a tire came apart or how much time I would spend on the side of the road waiting for a service vehicle

 

[rockyrhoads]

tire decisions

In looking at the data it seems that the extra width of the suggested tire would raise the front by 20mm and the rear by 22.5mm seems like a reasonable amount for the extra contact. I had not looked at the tire height before asking a question so thankyou phedre for correcting me. the front is accually higher from the factory by 6.25mm unusual but the engineers have a reason and I will not second guess that. I would guess that they want more downforce on the rear

 

[Phrede]

my friends at goodyear have given me my answer..245/35 front and 265/30 rear. I have 2 porsches and 2 late model stock cars with which I run hard on the track. This car will be on the street and the compound will be chosen for a mix of durability and traction in normal driving conditions. I will be sticking with the run flats as there is no room for a spare and since I have just spent 6K on body parts to rebuild this wonderful car I do not want to think about what would happen to it if a tire came apart or how much time I would spend on the side of the road waiting for a service vehicle

Let us know how that works out and if the 7% speedo error bothers the control modules.

 

[rockyrhoads]

Let us know how that works out and if the 7% speedo error bothers the control modules.

look phedre I am not stupid but if it makes you feel better to keep mouthing off then go ahead. I have had to replace all the modules in the car which requires a trip to the dealer for a reprogram and the new tires will be a factor in that. You have no Idea what I am doing here And I have thanked you for pointing out that the front was accually higher than the rear... Take your bow and move on

 

[Phrede]

look phedre I am not stupid but if it makes you feel better to keep mouthing off then go ahead. I have had to replace all the modules in the car which requires a trip to the dealer for a reprogram and the new tires will be a factor in that. You have no Idea what I am doing here And I have thanked you for pointing out that the front was accually higher than the rear... Take your bow and move on

I'm not interested in any bows. I have no intentions of bowing to you either or "moving on". You asked a question, I supplied information. You made a decision to go with what you wanted, fine. I wished you luck and asked for you to share the end results. I'm interested in knowing the results, no more, no less. If you choose to keep the results of your experiment a secret so be it. Don't get an attitude because I asked you to share the results. Again, you do not know me and don't know what I do or do not understand.

I do find it amusing that you wanted to know the widest tire and decided on something narrower than what many of us here are running currently based on what someone trying to sell you a tire has to say. Does your Goodyear friends offer run flat tires in the OEM sizes? Maybe they would loose your sale if you didn't buy these much shorter sizes, I don't know. It's your money, go for it.

 

[rockyrhoads]

I'm not interested in any bows. I have no intentions of bowing to you either or "moving on". You asked a question, I supplied information. You made a decision to go with what you wanted, fine. I wished you luck and asked for you to share the end results. I'm interested in knowing the results, no more, no less. If you choose to keep the results of your experiment a secret so be it. Don't get an attitude because I asked you to share the results. Again, you do not know me and don't know what I do or do not understand.

I do find it amusing that you wanted to know the widest tire and decided on something narrower than what many of us here are running currently based on what someone trying to sell you a tire has to say. Does your Goodyear friends offer run flat tires in the OEM sizes? Maybe they would loose your sale if you didn't buy these much shorter sizes, I don't know. It's your money, go for it.

and the question was about tire width on an 8.5 inch rim so as not to crown the tread and put undue stress on the sidewall due to pulling in the tire to the rim width. You read to much into a simple question and provide much more information than asked for. It seems that most people on this site are very friendly but as is in most cases every party needs a pooper ...you're elected

 

[Phrede]

and the question was about tire width on an 8.5 inch rim so as not to crown the tread and put undue stress on the sidewall due to pulling in the tire to the rim width. You read to much into a simple question and provide much more information than asked for. It seems that most people on this site are very friendly but as is in most cases every party needs a pooper ...you're elected

 

[Rob]

Ok, I'm jumping into the middle of this a little late. First off lets take a deep breath and calm down a little. Healthy debate can be good as it sheds light on education which is what we're all here for. If we can keep emotion and personal digs out of the debate...we can shed light on facts and truth.

I agree with much that has been said by both parties here, however I'm not able to speak from much experience as I don't own an XLR and have never tracked my ZR-1. I will say that you don't need super wide tires on the front end. Take a look at the 2014 C7 Corvette. The tires in front are smaller than a 2013 Grand Sport and yet because of the suspension geometry of the C7 vs the C6, the 2014 is able to run circles around the Grand Sport and achieve better lap times.

Sent from my SCH-I535 using Tapatalk 2

 

[Phrede]

Ok, I'm jumping into the middle of this a little late. First off lets take a deep breath and calm down a little. Healthy debate can be good as it sheds light on education which is what we're all here for. If we can keep emotion and personal digs out of the debate...we can shed light on facts and truth.

I agree with much that has been said by both parties here, however I'm not able to speak from much experience as I don't own an XLR and have never tracked my ZR-1. I will say that you don't need super wide tires on the front end. Take a look at the 2014 C7 Corvette. The tires in front are smaller than a 2013 Grand Sport and yet because of the suspension geometry of the C7 vs the C6, the 2014 is able to run circles around the Grand Sport and achieve better lap times.

Sent from my SCH-I535 using Tapatalk 2

No more comments from me on this thread. I have also added the other poster to my ignored list. Just not worth the personal attacks. I only wish the the forum supported complete blocking.

 

[Rob]

No more comments from me on this thread. I have also added the other poster to my ignored list. Just not worth the personal attacks. I only wish the the forum supported complete blocking.

Good. Because I've been receiving several complaints and this thread has gone in a direction that was unnecessary due to unnecessary comments and "wise cracks".

Everyone: state your points/facts as you know them and keep the snide remarks out.

 

[rockyrhoads]

so sorry

I apologize for any disrespect. The only question was the max width on an 8.5inch rim. I will refrain from asking questions or asking for advice. If any one cares to see this project finished I will post pictures of the progress and refrain from any further comments. If your wish is to have me blocked then feel free. This car is not intended the b be run on any track the tire width was for cosmetics only