[urq] Tire pressure for ice racing ?

[qshipq at aol.com]

 L-A
If you are looking to 'win' a competition, then the rear diff should be locked, as coming out of a turn apex it will give you more traction.  I won FTD in the 42 car SCCA Ice Rallycross at Steamboat in 97 using this technique on a borrowed 5ktq with Blizzacks (somewhere in the archives I did a turn by turn breakdown).  Basically, if you have a tight turn, just before the turn unlock the rear diff, and blip the throttle (unlocks rear diff), then at the apex, lock the rear again, and repeat.  Center always locked.

In my old 83 urq, I rigged up two late style electropneumatic rear diff switches to run the center and rear diffs.  The key is to have as much reserve vacuum (I added a vw eggcrate style vacuum accumulator tank) as possible, so that the diffs can lock and unlock when under boost.

All that said, for Steamboat, I just lock the rear all the time.  The trick there is to come up hot to all tight turns in a straight line, brake hard, then take the turn slow.  Or, if wanting to dance, you can just leave the rear locked, and go at it, like you can see me driving the track mars-urq in front of fellow urq lister Nate E in a 90q
http://www.youtube.com/watch?v=KfxjwHWuTzA

With a lot of sheer ice, the rear diff locked will always yield better control IMO/E.  If the cones are tight, it's not as easy, but good directional placement can be had by just a quick dump of the clutch (quick in/out to disengage the driveline, helps oversteer).

WRT 3000rpm, the technique I use is to keep the engine at 3000> all the time.  If there is a snow hook-up section, I'll run close to redline, which once traction is gained, keeps the car spooled up enough to not bog.  I used this same technique in a 90q20v at the 6900ft track, which worked just as well.


IMO/E 2 the Rsi and the WS50/60 are transparent in tractive ability (newer the better) for dedicated ice tires.  IMU, the Hakka Rsi is discontinued in favor of the Hakka R.  The Hakka R takes a step down in sheer ice for a step up in mixed ice/snow and ultimate snow traction.  BTW, just before Steamboat this year, we tied the center diff locked all the time, and I ran a new line from the IM to a ck valve to the diff knob, using the climate control vacuum canister as an accumulator, and the knob then only operated the rear diff.  Worked immediately and without fail for 4 days.

HTH and my .02

Scott J
84 Urq
83 urq ice track car


-----Original Message-----
From: Louis-Alain Richard <larichard at plguide.com>
To: qshipq at aol.com; laraa at sympatico.ca; vittorio at mybares.com
Cc: urq at audifans.com; quattro at audifans.com
Sent: Fri, Feb 12, 2010 12:32 pm
Subject: RE: [urq] Tire pressure for ice racing ?


Scott, why "good luck " ? You think I'll need some ? :-)



Never popped a tire, but I never ran lower than 26 yet. I'll bring the two sets 

next time, just in case I pop a tire. These are difficult to replace on the rim 

when temps are around 0F and there is no air supply close... Brady can 

confirm...



About the rear diff, when locked it makes the rear end very nervous under power 

but as you say, tight corners are a nightmare if you missed your approach. She 

just goes straight. And with that stock engine, 7:1 compression ratio, there is 

NO torque below 3000 rpm. I must play with the revs and the clutch to make the 

rear end slip in some slow corners.



So no one think that the Michelin will be any good ? 



Louis-Alain







-----Message d'origine-----



 At Steamboat Springs Ice track with the urq, we run between 24 and 26psi with 

WS50 Blizzacks.  For the urq on ice, the best pressure will be lower, generally 

24-28psi.  I run to the low end of that using innertubes, but it really depends 

on the tire size, a 205 on a fuch 15x7 will tend to pop it's bead when 

encoutering a snow patch at 25psi (btdt), but a 205 on a 6in rim or a 215 on a 7 

should be fine.  



The studded/bolted/spiked  tire will always have the advantage on an Ice track.  

At Steamboat, none of these are allowed, but usually in Ice racing competition, 

non-studded ice tires are in a separate competition category.  I also suggest 

that you run the center locked always.  I also run the rear locked, but can be a 

handful in a tight competition course.



HTH and good luck



Scott J

84 Urq

83 Urq ice track car