I put the re760's on the rear and bumped it up to the 275 width. In a straight line it is great. The extra rubber is awesome. But when I take highspeed ramps at 170 kph, the car feels way less stable. The car seems very bouncy. Not sure if it the size of the tire or the fact that I have pzero in the front and the stones in the rear.

Anyone else experience this?

The problem is that I still have tonnes of meat left on my fronts. I remember taking the same ramp with all pzero and the 255. And it seemed WAY more stable on the cornering. Hmmmmm

 

The problem is you're running max performance tires on the front, and what are essentially low-end UHP tires with good tread wear on the rears. Just go for some max or extreme performance summer tires for your next set (e.g., Nitto NT05, Bridgestone RE-11). Either way the rear tires won't last that long.

 

I am running 245/275 star spec right now and have been running this setup for 11k kms already. All I can say is the grip is miles ahead of the stock setup. When i say grip i mean both in a straightline and in the corners.

You might be feeling unstability for couple of reasons.

1) Its getting cold where u live and your tires ain't as sticky as before.
2) Taking mixed tire combo to the limit is a bit sketchy (i mean 170 off the ramp isn't exactly slow)
3) RE760 is not exactly an awesome tire, i mean its not bad but worse than Pzero,starspec,PS2,Nt05,RE11 etc
4) Check your tire pressure
Hope these info helps

 

RE760's arent the best tires. Next time get the bridgestone RE-11's or Dunlop Direzza star specs. I have the Hankook 275's and im not dissapointed at all.

 

Another possible cause is that I have nitrogen in the front and oxygen in the back? I would assume that might have an effect. I am getting the rears filled with nitrogen next week when I take the car to the dealer for squeaky brakes!

 

Sounds more like tire pressures are too high or the new tire compound is harder than the original or both. I don't see how the width itself could cause the bouncing.

 

Cold breaks = squeaky. Do a couple of hard 100km/h - 0 braking runs and I guarantee they won't squeak.

Also - not to be a 'dad' .. but you're a cowboy if you're drivin' 170k on a highway (on/off ramp or not) in this province.. $10k fine, loss of license and road-side seizure... worth it?

WRT your tire situation - running two different compounds is never the best idea. One thing with wider tires that you have to get used to is railroading.. happens all the time and is very unnerving, straight lines or corners. The RE760s really need to heat up as well.. the weather has been cold the past little while and that can have a major effect.

 

Thanks dad. Actually it is not really a ramp, it is an interchange between the 407 and 410. I have already been on the road for 30 min of highway driving, so they should be warmish.

I will give the brake trick, thanks.

 

+1... When i bought Yokohamas for the rear of my car and left the ps2 on the front i hated it as well on the highway. I was ready to just have the tires removed and sell them cause i felt like the car's *** was just floating and i didn't have full control. I let out 10 pounds in both tires and have not had a complant since beside the nail yesterday morning.

 

Also.. the use of oxygen or nitrogen, this has been hashed out many times.. http://www.straightdope.com/columns/...instead-of-air is a good primer on why not to bother with the expense of nitrogen (unless its free)...

One thing I noticed on bumping my tire in the rear (the previous owner had 235/40/18's on all 4 tires... *sigh* ) to 265/35 is that under hard acceleration, the back end feels a little squirly.. not as stable as the 235's.. might have something to do with the "railroading" reference someone made, but I am not clued up on that.. going to go research it now

 

dont mean to be "that guy" - I take the 407 every day as well and the car just wants to go faster.. I just can't do it, it would be just my luck that the one time I go above 150 there would be OPP sittin' right there waiting.

I'd say then that what you're feeling is a combination of everything discussed here

a) different compounds front and back
b) tire pressures, etc
c) some railroading
d) just getting used to the different "feel" of the new tires

 

Railroading can make the car feel REALLY sketchy.. almost like hydroplaning. The wider the tires, the more often an more pronounced it gets. On my corvette the tires are 265/295 so you can imagine it's really exaggerated. Going straight on a well-work highway can create some nervous moments.. the car will feel like it jumps to the left or right as the tires move in and out of the grooves. Even though you might not see the grooves in the road.. they are there.

 

Sidewall stiffness...

I noticed it also when switching to 275's on the Hanook's.

 

just switched my rears from 245 to 255 and I once I speed up It feels like I am floating... maybe my car just flies

but in all seriousness I wonder why

 

What pressure are you guys running for the road?

Also my balancing is off. Taking it in tomorrow to get that redone. The tire guys says that happens if the tire didn't set before the enormous torque kicked in.

So I guess I have many things to check out to resolve this issue.

 

well to be honest I dont know what pressure their set at. When I purchased my wheels I took them to carlsson and they balanced,mounted, and filled the tires for me

other than slow speed and take off grip my stocks felt better around the corners

 

The floating feeling may be caused by the rear's "hooking up" and causing the front to slightly rise up.

I felt this feeling after I put on the MT’s. Every time I got into the gas the front felt very light almost like it was floating…

 

Don't think that is it. Cause when I am in the corner, I am at constant speed. No acceleration.

 

I'm pretty sure you have some kind of acceleration(change of velocity) during a corner or else there would be no importance of corner entry and exit speed

 

Floating front sounds like understeer to me...wider rear will cause more understeer on the car.

 

maybe its because I am running 235 front and 255 rear, I am actually supposed to run 225 up front.

 

225 up front?? I thought stock was 235 up front, not 225...

 

no on a w203 stock set up is

225/45/17
245/40/17

I now run

235/40/18
255/35/18

if anyone is interested in my front tires let me know they are less than a month old with receipts to prove it. Vredestein ultrac sessanta for a hella price.

 

I took the car back to the tire guy. He rebalanced the rears, replaced the oxygen with nitro, and reset the tire pressure. It does feel better on the city streets. I will see tomorrow on my interchange corner if it handles any better at the high speed corner. And I think my stock fronts are 235.

 

Yes your stock fronts should be 235/40/18.