924Board.org

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Need to know whether these tires would work, front and rear, on 7x15 cookies with rolled fenders.

If yes, are you running coilovers or spacers? What about lowering springs or torsions in the rear?

Thanks!

924RACR · Posted: Wed Nov 23, 2011 10:31 pm Post subject:

We did, but the fronts needed a bit of flaring as well as rolling.

With the late-offset PD's, no rolling needed.

Coilovers (2.5" springs) up front, t-bars only in the rear.

Now we're required to run 6" wide rims (per class rules), so stock 924 15x6" rims.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Thanks. I have access to low heat-cycle hoosiers from some of the 944 cup guys and they're running the 45's. Was hoping to take advantage of that but it looks like maybe not because I'd have to run 7x15s....

Back to the 6x15s

924RACR · Posted: Thu Nov 24, 2011 11:39 pm Post subject:

Perhaps I should clarify.

We are now required (in ITB) to run no wider than 6" rims, so we run the 15x6's.

I didn't say we stopped running 225/45/15's.

We continue to run the 225s; it's just a little more work to get the 225's on. More work for the tire guy, that is.

Go for those cheap takeoffs.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Ho! You're running the 45s on 6" rims? I've run 225/50s on 6" for years but not 45s. How's the contact patch look? What pressures are you running?

I ass-umed that 6" wouldn't work because of what hoosier says about minimum rim width...

Tell me more...

924RACR · Posted: Sat Nov 26, 2011 11:30 pm Post subject:

They're fast. This is the config in which I've set both Mid-O lap records, won the Waterford Championship, and various other such things.

Standard drill, target hot pressure is 39.5 psi. Cold pressures, YMMV, depends on ambient and how hard you push, could be anywhere from 28-32psi.

We of course picked the size, in part, because of the plentiful takeoff supply.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Schweet. See ya at the track

Fifty50Plus · Posted: Wed Nov 30, 2011 2:07 am Post subject:

I was running the 225X50X15 HoHos on both the Benz and 911 (7 inch rims) for a few years. Has a bit of a rear fender issue on the 911. Switched to the 45s on both cars. Both are now 1/2 inch lower to the ground and the wheel revs/mile has gone up a bit (better acceleration). It also slightly changes your effective spring rate. I like them and as Vaughan said, I will put them on the 924 on 6 inch rims.
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Ja, I've been running 225/50's for years. The thing that had me concerned was Hoosier says "no narrower than 7" rims" for the 45's. I gonna say experience trumps their guidance however

I'm hoping for all the benefits/changes you mention (gearing, lowering, spring rate...) and see little on the downside.

Still two concerns however which I guess I'll have resolve for myself:

1) Rubbing somewhere, which is fixable IMHO. The 50s *just* touch in the front under hard cornering (45s will have lower profile so that might solve itself...) The fenders are already rolled/flared but the car is lowered, but i might have to go with coilovers in the front and remove the spacer in the rear to clear. Gonna load up some koni sports and that might help some too as that should reduce the suspension movement a bit...

...and the other concern is having the sidewall tucked in so much that it compromises either tire sidewall strength or the flatness (size) of the contact patch against the ground...I'll just have to see what happens there and perhaps manipulate the pressures after taking tire temps -- that'll tell me straightaway what's going on with the contact patch...

924RACR · Posted: Wed Nov 30, 2011 5:03 am Post subject:

We actually use doubled-up stock rear wheel spacers on the rear, and singles on the front (bored out to fit the front hub).

Sounds like you need more suspension stiffness/less roll...

EDIT: here's a pic of the front:

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

emoore924 · Joined: 13 Apr 2004 Posts: 2822

What wheels are you using tho? You're moving things out pretty far. I thought you'd mentioned at one time you were using late phonies. I have like a million cookies..., and stock length wheel studs I think.

Fifty50Plus · Posted: Wed Nov 30, 2011 1:16 pm Post subject:

A million cookies....Yum
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

924RACR · Posted: Wed Nov 30, 2011 10:46 pm Post subject:

LOL!

No, we run 6's, remember? These are stock 924 5-lug 15x6 spiderwebs.

As you can see, yes, we did have to fit longer wheel studs.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

SoyRacer · Posted: Sun Dec 25, 2011 10:53 am Post subject:

Okay... I have run Hoosier 225-45s on 15x7 cookie cutters for several years on the track rat 944. They are dirt cheap second hand and almost as cheap as new Kumos. They are a tight fit on the 924 15x6 phones/spiders and behave almost like cantilever tires when the sidewall is so drawn in. I usually start them off at 30psi for a hot temp of around 38psi. I run turbo sways on stock suspension with koni inserts/koni adjustables. Weltmeister 250s made a difference up front. I ran 205s but it was a different drive. Not better or worse. Just different.
_________________
1973 911-RS 3.2 Track Car
1981 Porsche 931/Carrera GT Project
1981 Porsche 931 Euro W/CGT Intercooler
1984 Porsche 944 Gutted Track Car
1987 Porsche 924s Rally Style (sold 3-2012)
2000 Chevy C-2500 Pick-up
2004 Subaru Forester STi

emoore924 · Joined: 13 Apr 2004 Posts: 2822

What does this mean "cantilever tires"...??