Darien

Here's some I took this morning. I'm looking for opinions on how they look. I think it's too much rubber for the 9" Cups, (P275/40ZR-17 Sumitomo HTR ).

Also, I haven't upped the size of the fronts yet, so they are 205's. Not sure what it is, but the car feels very sluggish now. On the way to work, I had to get on the breaks to dodge an idiot that pulled in front of me and I felt like I was all over the place Last night driving home, I could feel the same bouncy feel taking curves at normal speeds

animal8526

id check the PSI they look overinflated!!! other than that they look good!!!! as for slugish.. is the OD dif,? ie: are the new tires taller?..even if not the fact that they are heavier will make them seem just a tad slower. one way to counter this is to go with a shorter tire.. ie: 40 series instead of a 45 series.

dr bob

Those rears look really tall, and maybe just a tad overinflated. Try 36PSI +/- to start, and look to see if you have good contact (chalk test) along the sides of the tread area. Measure the circumference with a cloth tape, and derive the rolling diameter from that. Compare with fronts and see if they are within 1/2" or so. The "dust" patter on that rear tread in the picture looks like the outer ~~3/4" isn't even touching the floor.

On the 205 fronts-- Swap them for --AT LEAST-- 225's as soon as you can justify it. I drove on the 205's that came on my takeoff 996 wheels. They were "fine" until I changed them up to 225's. Probably should have gone to 235's on the 7.5" fronts, knowing what I know now. The 225's made a world of difference. 235's would be two worlds better.

Darien

Right on... I'll definately address the PSI I was thinking about 235's but wasn't sure if they would stick out too far.

Darien

Well, the tire shop had 41 psi in the rears. I got them both at 36 psi. On the way home tonight, it still felt very squirley, it's actually a little scarey Can having wider tires on the back and skinny tires on the front cause that sensation? With the 255's it felt fine!

tommytomaso

Darien....check the tirerack for your tires and see if others have complained about tread squirm!!! its a problem that iv seen in some consumer reports , and the TIRERACK is a good place to check if your tires have this issue... My winter tires at anything above 40degres realy have a bad squirm...feels like driving on jello.
do i dare say.."CHECK THE LUG NUTS""

Darien

I got the tires from Tirerack As for the lug nuts, I don't let the tire shop touch my Shark. I take the wheels off at home and take the wheels and tires to the shop. "Jello" is a good word to describe the feeling I'm having

SharkSkin

You really need a 35 series tire with that width... they are taller, giving you taller effective gear ratios -- more sluggish.

Also, 36psi is still too much IMHO. Try 28-29 psi.

Darien

I asked Tirerack about 35's and they didn't have them I've read about others that went with the 275/40 and no complaints. 28-29 psi okay?

sharkmeister85

My understanding is that tires beyond a certain size increase need to have the Weissach axle pinned or the result can be very dangerous handling characteristics. Sounds like what you're finding.
Glenn

SharkSkin

There have been plenty of debates in these parts about tire pressure. I have 255/40/17, and the last set wore faster in the middle -- with 29psi. Now I run 28psi. A wider tire ought to be fine with these pressures, but of course YMMV.

928SS

iirc, the axle pinning was an issue on cars that had wider tracks/more offset to keep the tires from rubbing on flares etc.

my 295x30's have no squrim or bad habits. but they are on 10.5" rims. if your tire is still rolled up on the sides even w/lower pressure, the 9" rim could be causing them to roll up and act weird... 40 is kinda high for a super tight feel, IMO. my old 225's were 40 series also, and the diff is night and day (more solid/less sidewall flex) w/the lower profile...

also if you've gone to a higher tire from a lower profile just in the rear, it could change your alignment a bit by changing the car's attitude (ie more foward down) which could also cause some handling oddities...

anonymousagain

okay, just curious <Sharkskin you may already use this?>, but from my 4-wheeling experience, I've always followed the recommendation to calc the <street> pressure according to: (max load/max psi) x 4 = psi ratio; (vehicle weight/psi ratio) = street psi/tire

My shark runs 245/50/16 Daytona's (Fuzions) and I figure ~3700lbs<including me and the misses>: (1609 load/51psi) x 4 = ~126 ratio; 3700wt/126 = ~29psi.

Should I reconsider using the calc method? You guys are talking in the mid-30psi range, is that because of higher performance/extreme considerations?

SharkSkin

I arrived at nearly the same numbers using purely empirical methods. I got in the ballpark by drawing a chalk line across the tread and rolling forward slowly to check how the chalk wore off. After that I fine-tuned with an IR thermometer, checking temps across the tread after several miles of highway driving. Once I felt I had it right, I let it sit overnight and checked cold pressure in the morning. Hot, the pressure was in the mid-30's. Also, observing tire wear figured into it. I arrived at 30/28 psi cold, F/R. 225/45/17 Front, 255/40/17 Rear.

anonymousagain

whew, I'll stick with the calc method for the shark as well then (seem to be wearing square as expected thus far as well); good to know the chalk method though, especially if mods for weight +/- have been done. thanks Dave !!