mark kibort

Thanks. It worked out great. NO BODY WORK DURING THE OFF SEASON!!

Cant wait to try it out tomorrow at the NCRA track day at thunderhill!

mk

mark kibort

I have one set of rims that I had made with 10" widths, instead of 9.5" up front for this reason. backspacing is .5" further, so from the side, there is no difference when using the same size tire.

So, yes, the tire size is the 305x 35s that i normally use on the rears. with spacers now, i can run the 275s normally in practice and for commuting to the track. the 305s might change everything. im wondering what the .5" ride hight increase will cost. Ill do a corner balance when i can to see what changes. I have a feeling that the extra meat up front will be a HUGE difference.

Ill let you know after tomorrow.

mk

Benton

Cool stuff! I was thinking you should try this before paying the big bucks for aluminum work. I'll be making some fiberglass front fenders for the front of my car in about 3-4 weeks to match the steel work I did on the back. I'll be making a mold, so I could probably make a set for you or anyone else interested in the future if interested. I'll post up once I get the project started... I'll be widening my Kinesis wheels with forgeline halves. I'm probably going with about 2" wider per side, 11" wheel, 7" backspacing-ish. I have the exact numbers written down with F/R track widths and what not, but it's not with me.

IcemanG17

MK
let me know when you need the tires.....

How did it go....?????

Fabio421

Jim Bailey did this to his car. He has spoken about it a couple of times here on Rennlist.

Constantine put 305's up front on the Coke racer without mods. I think he ordered the wheels to have the exact offset and you lose a little of the extreme steering lock but if you ever need that part of the steering in a race you are already f@cked

Mark, show us some pics where we can see how wide the tires are.

mark kibort

Here are the pics.

the passenger side had no real issues, and it was the outside tire for most of the turns, but there is a "corkscrew" like turn that compressed the driver side and it hit the top of the fender and burned the paint. on the driver side, i have my old injury from rubbing with the S2000 in a race 2 years ago. that might be why its rubbing, but its very close. I might be able to move it out more, but the hitting up in the fender is a worry. Laguna would crush the suspension and make this issue a real problem.

Bottomline, the difference was not as great as i had hoped. my laps times were the same and the car felt actually more turney with the smaller tires up front (275s) it could be due to the 305s pinched on too narrow of a rim, or the front now .5" higher (tires are 1" taller). car still pushed, and actually it felt like it pushed more! the contact patch might be the same as from the wear patterns, it looked like at least 1" of the outside tread wasnt even used.

mk

Benton

Well, it looks badass! I think it is a combination of both factors. If the wheel were wider, I don't think the tall sidewall would be much of a concern. However, since the tire is a bit pinched, that makes the tall sidewall even more apt to roll over the rim and get a bit squirmy. I could see that tire taking longer to set after turn-in. ??

Toyo lists an 11" wheel as ideal, and even a 12" at the high end. As the sidewall height increases, the recommended wheel width increases for the same width tire.

So what are you going to do now?

dprantl

The way it looks now, it could be pretty easy to slip a metal rod in there and roll the fender using the rod/tire after the car has been in the hot sun for a few hours.

Dan
'91 928GT S/C 475hp/460lb.ft

mark kibort

They have already been stretched as this is how it looks normally anyway, its just now, i have the angle up front where there is some rubbing. it also might be due to that fender being pushed in a bit due to the racing contact a few years ago there. however, the hit on the fender with the tall tire worries me, as down the corkscrew at laguna if it really hits hard, it might lock up the tire or just burn the paint even more.
Ill put that wood dowel in there and see.
currently, i have my 275s with even greater spacers (normally 1/8" now, .5") to simulate the same tire position on the fender. it rubs, around the padock, but not on the track. but its like normal set up with the fenders in stock position. I can see if i can get any fender movement with the bat

mk

mark kibort

i had the same set up on the rears when i used the 335s on the 11s, and it worked but it didnt seem like the sidewalls worked enough. same up front with the 10s and the 305s. they just seemed like they were not working as well. could also be that the pinched sidewalls, brings down the tread sides and you end up with less contact patch. could be equivilant to the 275s which are exactly 1" narrower than the 305s normally. the tire sets on turn in, but just doesnt have the grip i would expect from a larger tire.

dont know what im going to do now. since my times were the same, but didnt really have a chance to really push them hard, i might give it one more shot and move that fender out a little somehow. it did do something that never happened before at thunderhilll. at turn 6, there is a sharp 100mph kink. i usually yank on the wheel to get the car to slide 4 wheel through it. doing this on lap 2 of the race, induced a huge over steer. got it very sideways through it but recovered. (the 928 is awesome in a slide). the increased grip up front caused this, so maybe there is some gains yet to be realized with this bigger tire. over all though, it wasnt a big difference. that could have been due to my very old commuter /practice tires i was working wiith during the day. 20 heat cycles and 4000 street miles!

mk

Jim bailey - 928 International

You want the sidewalls to be like this l l or a bit like this \ / but you never want them like this / \ . Which is why most rules just state maximum RIM WIDTH and let you run any width tire you wish.....the guys with tires too wide just go slower With the sidewalls like this / \ the rim when it pushes sideways will actually cause the inside sidewall to lift part of the tread off the road and is very unstable as well. Sidewalls like this \ / give very sharp turn in and good stability since it is very hard for the rim to move sideways relative to the tread since the outside sidewall is already under tension.

mark kibort

sounds what i have being the / \, its not very good and one of the reasons i didnt like it too much. the 80mph sweepers were just as pushy, and was even more like a "plow" in feel .

as i said, the times were still as fast my fastest, but i didnt like the feel as much and the rubbing noise was like fingernails on the chaukboard.
interesting, i was still able to get to near 135mph on the main straight so the extra rolling inertia of 5lbs per side wasnt really noticable.

mk

hacker-pschorr

I have no idea what you guys are talking about, I prefer this: ( . )( . )
Or maybe (o)(o)

Even better

.(o)(o)
. ) ..(
.( .Y .)

mark kibort

/ \ would be showing that the tire is wider at the road contact than the point where it fits to the rim. these would be the sidewalls looking straight on.

Now i have no idea what you are showing with the (.) or the (o).

edit: oh.... he he, i get it.

mk

Jim bailey - 928 International

If you ever drive a truck with 15 inch riims and big oversized offroad style tires the whole truck will float side to side as you go down the road as the rims move side to side relative to the tread with just minor steering corrections. The combination of tall soft sidewalls AND / \ pinched in at the the rim makes it feel really bad. And yes the GT3 911 is an amazing "street" car I instructed a student with one and loved the POWER ! As always I opted NOT to drive his car but I was very tempted just did not have a spare $150,000 to pay for it if I crashed it