mixed tire setup F/R ??

[cojones]

Considering running this setup:
- FRONT 215-40-17
- REAR 275-40-17
TCS should be fine: F/R ratio is 7.9% (versus 7.7% for OE 91-93)

Considering running different tires front to back. Both are STREET compounds, but the REAR (YOKO AVS Sport) is a little grippier than the front (TOYO T1-S Proxes). While this SEEMS wrong, its an attempt to emulate the OEM setup with a softer compound on the REAR.

Comments and suggestions welcome? I already have the wheels and tires, so its a "free experiment".

[This message has been edited by cojones (edited 06 May 2002).]

 

[SNDSOUL]

I ran that exact tire in the rear of mine and it worked great. I used Yoko 520's in the front no problems.

 

[cojones]

Just to clarify -- I've already run these tires before, and they fit and work great.

Will running a TOYO T1-S front and an AVS Sport rear cause any handling problems ??

It'll be mainly for Driver Ed road-course driving (including lapping days). 45 minute sessions max.

 

[cojones]

any advice on this ?? Specifically for TRACK use ?

Someone told me that the OEM rear tires have more than just a "softer" compound; their internal construction (belt pattern, etc) is actually "optimized" for the car. Sounds like marketing brochure-ware poop to me

[This message has been edited by cojones (edited 07 May 2002).]

 

[nsxtasy]

Originally posted by cojones:
any advice on this ?? Specifically for TRACK use ?

I wouldn't intentionally run tires with significantly different grip characteristics.

Originally posted by cojones:
Someone told me that the OEM rear tires have more than just a "softer" compound; their internal construction (belt pattern, etc) is actually "optimized" for the car. Sounds like marketing brochure-ware poop to me

No, it isn't. Manuel, check out the "Tire Tech" section of the FAQ.

 

[Forums Nazi]

Also, sjs posted an interesting description of how the biasing and compounds of the OEM tires work with the NSX alignment here.

 

[cojones]

Anyone with SPECIFIC experience with a sticky FRONT and a stickier REAR in 17/17 or 17/18 sizes (aftermarket tires)??

ICBW, but the tendency to run 'balder' rear tires relative to front tires (typical with NSX relative tire wear rates) tends to create this situation even under "factory recommended" use, no ??

Does anyone know if the new 17/17 setup (Bridgestone RE040) has the same front-rear "special" staggering (tread compound and tire carcass design) ??

 

[nsxtasy]

Originally posted by cojones:
Anyone with SPECIFIC experience with a sticky FRONT and a stickier REAR in 17/17 or 17/18 sizes (aftermarket tires)??

ICBW, but the tendency to run 'balder' rear tires relative to front tires (typical with NSX relative tire wear rates) tends to create this situation even under "factory recommended" use, no ??

No.

I assume you are implying that balder tires are stickier. They are not.

People think that balder tires are stickier because treadless slicks are used in racing. However, slicks are stickier because they use softer compounds, not because they are treadless.

 

[Ponyboy]

I believe the implication is that the bald tires could have more tire contact patch with the road and therefore sticker.

Is that right Cojones?

 

[cojones]

Originally posted by Ponyboy:
I believe the implication is that the bald tires could have more tire contact patch with the road and therefore sticker.

Is that right Cojones?

That is correct... this is what I've been told by several experienced racers that save their balding street tires for a race. Less "gaps" means more rubber on the road for a given size/shape of contact patch

This is also why they shave street tires for spec-series use (e.g., they use a shaved TOYO T1-S tire for the Speed Channel World Channel).

I am aware of what R-compound rubber does to adhesion... these softer compounds offer a much higher coefficient of friction than street compounds. Also explains why they pick up so much crap in the paddock

 

[cojones]

Originally posted by nsxtasy:
I assume you are implying that balder tires are stickier. They are not.

Most racers have told me otherwise. See above.

Compare F1 dry tires with rain tires for an example...

 

[nsxtasy]

Wow, lots of misinformation getting posted here.

First, the reason that less tread is better is not because of a bigger contact patch. It's because there's less squirm in the individual tread blocks when they're not as thick.

Second, tires that are worn down are not very sticky. In part, this is because of the hardening of the rubber compound as the tire is used. That's why experienced racers have their tires shaved, instead of using worn tires. There's a huge difference between the two. As stated on the Tire Rack website:

One of the reasons radial racing slicks are so effective is because they feature shallow tread depths and their contact patch acts as a single unit. However, any tread design breaks up the contact patch into smaller elements and additional deep tread depth (required to enhance wet traction) allows tread block squirm which will reduce dry performance. This means that tires typically provide their worst wet traction ... and their best dry performance just before they wear out. However, its also important to remember that the heat generated every time a tire is driven activates bonding agents in the rubber. As this process is repeated continually throughout the tire's life, its rubber compounds gradually harden and loose flexibility reducing the tire's grip. Therefore, a shaved "new" tire will provide more traction than a tire worn to the exact same tread depth after being driven for thousands of miles on the road.

[This message has been edited by nsxtasy (edited 16 May 2002).]

 

[cojones]

Originally posted by nsxtasy:
This means that tires typically provide their worst wet traction ... and their best dry performance just before they wear out.

cool... the above info is EXACTLY what I've heard many people -- who've actually tried it -- say about used tires.

Tire Rack's motivation is partly to sell new tires, not encourage "Team Cheap".

I'm just exploring the possibilities.

 

[nsxtasy]

Originally posted by cojones:
Tire Rack's motivation is partly to sell new tires, not encourage "Team Cheap".

I've found that Tire Rack consistently provides the very best tire advice around. Sometimes they provide advice that helps them sell tires, and sometimes their advice actually discourages tire sales. I have never, never, never heard of a single instance in which they have seemed to provide advice that was designed to increase their sales.

I recently had a need to verify something. I contacted one of their top technical people and he was happy to spend time on the phone with me discussing the issue.

Tire Rack also supports local club events, through direct sponsorship as well as raffle prizes and the use of their facilities.

Yes, Tire Rack sells tires. Their prices are very good, and their customer service is as good as any business I know. I can't think of a higher compliment for any business.

Manuel, your slam on the Tire Rack is entirely unfounded and uncalled for.

[This message has been edited by nsxtasy (edited 16 May 2002).]

 

[Soichiro]

Manuel asked for information on the grip level provided by worn out (bald) tires.
Ken responded with some info:
>>... their best dry performance just before they wear out.<<
And Manuel responded by saying great, that's exactly what I was told (implying that bald tires have good grip). THIS IS WRONG.A TIRE IS WORN OUR WHEN IT REACHES THE END OF THE WEAR BARS - WHICH IS BEFORE IT GOES BALD. BY THE TIME A TIRE IS BALD IT HAS VERY LITTLE GRIP. This is consistent with my race experience over the past 2 years - a new, shaved, heat cycled tire has lots of grip. The grip declines rapidly as the tire wears. By the time its bald (about 800 miles for my Kuhmo Ecsta 712's) it has very little grip in the dry and NO grip in the wet. TIRES IN THIS CONDITION ARE EXTREMELY UNSAFE. Make sure you get advice from someone with experience, like Ken or a professional at The Tire Rack (or other reputable vendor) when making decisions like this about your vehicle. Advice from someone who *thinks* they understand what they are discussing, but is really only *conjecturing* on what might happen, is foolhardy.

 

[Soichiro]

Manuel posted another 'reason' why bald tires have more grip than treaded tires:
>>Compare F1 dry tires with rain tires for an example...<<

Manuel - what is the source of these 'facts'. According to The Grand Prix by Setright or The Art and Science of GP Driving by Lauda or Technology of the GP Car by McKnight the reverse is true. A dry F1 tire lasts about 100 miles in dry conditions but a wet one lasts about 10 miles in the dry because it's so much softer and has so much more grip. That is why you see F1 drivers looking for wet patches (to drive thru) when the weather dries after a wet start to a race - if they don't cool their (soft, grippy) wet tires in this manner they wear out immediately.

 

[cobalt]

I've run both of these tires before...they have similar break away characteristics...

The AVS Sport is slight more grippy than the T1-S...so I'd guess you'd just understeer more with this setup...so mess with tire pressures or sway bar settings OR your Koni settings: firm up your Koni's in the rear.

-Andie

 

[cojones]

OK... lets go back to my original question...

Two different street tires, rears (Yoko AVS Sport) slightly grippier than the fronts (Toyo T1-S Proxes). Not "night and day", or "R-compound vs street" or "bald versus shaved".

Several very CORRECT reasons have been presented as to why NOT to do this. And I tend to agree with them all... source-independent (I agree with physics / deformable-body dynamics, and the materials science as well as the next guy).

As such, I still have some spare tires I'd like to try out.

Based on track experience, would you try this combination on-track??

Assuming you'd forego the "sage advice" [I believe the Tire Rack IS the truth here], what factor(s) would you consider in mediating the grip differential?? To constrain this, assume we can only play with tire pressures and shock stiffness?

Grippier rears suggests a tendency towards understeer (forward rear grip overpowers turning front grip). You can counter this with ... ???

 

[nsxtasy]

Originally posted by cojones:
OK... lets go back to my original question...

Good idea.

I know some people say that you should never mix tires, with different models front vs rear. That's one opinion.

I would cut some slack from there. I think it's okay to mix tires as long as (a) every driver of the car is aware that there is a possibility of handling different from stock, and (b) the tires are very similar in their characteristics. For example, as long as the driver keeps this in mind, I think it's okay to have the OEM Yokohama A022H on one axle and the OEM Bridgestone RE010 on the other axle. It provides a way to transition from one type of tire to another without having a pair of tires go to waste to achieve the transition. I myself have tried using Kumho V700 Victoracer R compound tires on one axle and Yokohama A032R R compound tires on the other axle for this reason, with successful results.

I don't think it's okay to mix tires with significantly different grip characteristics. It's just too unpredictable; there are too many ways in which they can differ. (For example, they may differ in one way on dry pavement, another way on wet pavement, and another way on the track.) And it's even more unpredictable to try to compensate with those differences by adding still more differences to the equation, which is what you seem to be intent on doing. The last thing I would want to do is to be creating a situation where I'm going out on the track with absolutely no idea how the car is going to handle.

At the track, tires are the most critical part of the car, for they affect everything the car is doing. Just to give an idea of how critical tires are, a week ago I drove my other car at Road America. Manufacturer recommended pressures are 35F/33R cold. I wanted to try using slightly lower pressures so I had 30 psi all around on my A032R tires. The car handled horrendously! Every turn, it seemed like it didn't want to go where it was pointed. The following session I returned them to the recommended pressures and it was wonderful. If a few psi of pressure can make that much of a difference, using tires that are significantly different can be even more so.

Bottom line, for me, is this: I wouldn't use significantly different tires on a car, I especially wouldn't use them on the track, and I especially wouldn't try to throw other variables into the mix to compensate. It just sounds like an all-around bad idea to me.

$.02

 

[ck]

Just wodnering...

How do you shave a tire, anyways?

 

[Soichiro]

Tires are shaved with ..... a tire shaving machine (Doh!). These are long blades that are pushed against a spinning tire. BTW you can only shave new tires - a used tire has too much grit in it and will destroy the blades. Tires are heat cycled by being run up against a series of rollers at pre-determined levels of friction. Tires must be cooled 24-48 hrs. after heat cycling for the process to be effective.

 

[nsxtasy]

Originally posted by Soichiro:
Tires must be cooled 24-48 hrs. after heat cycling for the process to be effective.

Cooled, meaning, not being used during that period. If you order tires from a place like the Tire Rack or Discount Tires Direct, they cool while they are in transit to you.

 

[Ponyboy]

Wow, lots of misinformation getting posted here.

First, the reason that less tread is better is not because of a bigger contact patch. It's because there's less squirm in the individual tread blocks when they're not as thick

Wow indeed. I think that statement was directed to me. That's an entirely true statement and it's pretty obvious. Less tread is better because there is more of the tire contacting the road. That is one aspect, among, a few of why it's better. If less tread didn't do this people wouldn't run slicks and instead run shaved rain tires.
I'm not saying less squirm is not an issue, it is to a degree, but to just entirely dismiss other aspects is pretty narrow. . .ah, nevermind.

 

[nsxtasy]

People don't use slicks because they have no tread. People use slicks because they have an ultra-soft, ultra-sticky compound.

Tires worn till they're bald don't grip well. Period.

Round and round we go...

 

[Ponyboy]

Yes, obviously. And they get more of that compound on the ground when there isn't a tread there.

Sounds like a good question for your TireRack friend.

[This message has been edited by Ponyboy (edited 17 May 2002).]