DJWorm has again provided informative counsel for us “weekend” DE’ers in his posts for the “road racing weak points?” thread. His contributions truly make Z06Vette an outstanding source of information.
I have a couple of questions:
1. I have 19” wheels with 295’s on the front. Having removed the stock ducts, is there a way to install LG’s spindle duct and 3” hoses w/o L/R full turns damaging ducts?
2. Does his caution “DO NOT fall into the trap of using HP street tires on the track.” preclude Michelin PS2s? I have 20” rears with 335’s on 12” rims. I am upgrading to Brembo’s front and rear.
Jim,
In answer to your first question, here is something you can do to help the longevity of the DRM brake ducts.
In SCCA T1 I run 315/35-17 on 17x10s and they rub the ducts on sharp turns, which mostly occurs maneuvering in the pits. To help prevent wear where the tire rubs on the ducts, I wrapped Kevlar strips around the outer edge of the ducts. Laying Kevlar strips is much like using fiberglass, something I am not proficient at. But I found this doable for the Sunday afternoon mechanic that I am.
Jim,
Yes. My DRM ducts are always in the car. On street tires (stock wheels) there really isn't an issue. I added only about three half overlapping Kevlar strips to the DRM ducts where the tire rubs on them. This only added about 1/16" - 1/8" thickness increase to the DRM duct, which is insignificant. The kevlar is extremely resistant to wear. I put duct tape over the kevlar strips, which I look at every time I have my wheels off. I can see the tape is getting worn through, as I said, mostly from lock to lock turns in the pits, but the kevlar hasn't worn at all. Next time I have my wheels off, I'll try to remember to take a picture.
I took this picture to show how I slip heat shielding around the tie rod ends, the front passenger side in this case. But you can see the DRM brake duct clearly with the duct tape covering the kevlar strips. You can also see the big arc in the middle of the tape showing exactly where my tire rubs on the duct.
Pardon the dirt... this photo was taken after the car had driven into my brother-in-laws garage through a huge mud puddle after one of the hurricane's swept through Norfolk last Sept.
That Kevlar trick is a very shrewd "track fix". My compliments.
You can also run an "under pan" primary or auxillary scoop either ahead of the front spoiler or thru the front spoiler with flexible ducting.
The reason I do not like street tires or so called HP Street Tires with "R"??? compunds on the track are as follows
1. Generally these tires are expensive and have higher wear rates on the street. $250-$450/tire range
2. On the track they wear even faster.
3. Because of the tread block pattern, design and softer compound they give an immediate better response on the street but DO NOT perform up to expectations on the track.
4. On the track they heat up faster and can not dissipate heat, they will blister and shed cords and delaminate.
5. The tread blocks cause the tread to "shimy" and deflect and handling really isn't that good
6. To respond better they need to be shaved to at least 4/32 to start. While this increases their performance it decreases there overall life
7. They are heavier than true A or R tires
8. Most novice drivers learning curve quickly goes beyond their performance and the drive gets frustrated real fast. Now he needs true A or R tires and a new set of street tires.
9. When you switch to A or R tires the learning curve starts over
Why not get the correct tires for the track to start with, save your expensive street tires for the street, learn on the track on the tires you will be using on the track, have the performance you need, and save money??
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Thanks DJWorm, you are so right as the PS2's are very expensive and wanting to attend 3-4 DEs a year seems prudent to invest in "track wheels and tires". Can I use the stock 18's on the front and only buy 18's (?) for the rear to accomodate the Brembos?
Found an earlier post that appears to speak to my question:
"It should also be noted that the 305/30x18 and the 315/35x17 are almost equal in tire width and are equal in overall diameter. This does not cause any AH or TC problems as the delta is not greater. (I run with them off anyway, except in the wet of course)" DJWorm
Does this mean I could reverse the OEM wheels and mount indicated above racing tires and still accomodate the Brembos?
You could but I do not recommend using the OEM wheels on the track.
You are better off using race wheels which are lighter and stronger. Also note that I run these wheels and tires (305/30x18) on the front with an SCCA allowed +0.25" offset built into the wheel.
A racing wheel can also be repaired much easier and cheaply than an expensive OEM wheel should an off course excursion be experienced. Save the street tires and wheels for the street.
The newer DRM duct fit a bit tighter than the first generation. I run 17 x 275's and 18 rim with 25.5 x 11.5 and have just about no rubbing problem. I put some duct tape and it just may have a few nicks after 2000 + track miles I never used to be able to go lock to lock with the older style ducts. Critical where you postion them when installing them. Kevlar is a good idea. The red hose slips right into the duct and black hose. I have a PVC ring pop riveted inside as a stop. I could swap the hose by just pulling the hose clamp and slipping the hose out. Worked good for a few thousand track miles SCEET( I think that's the designation I always mix them up) hose is worth the money.
Speedpup,
Thanks for the info. My DRM ducts were bought about Jan 02 and have survived something like 4-5 DE days and 24+ SCCA races with the kevlar "fix", but the newer ones look nice.
Speedpup... man your setup looks so nice and clean. I'm about to order the Bilstiens too along w/ the ducts and spindle ducts... holding off on the T1 bars for now.
So far the hot T-1 setup for road racing are CCWs 18 front and 17 rears? What size wheel and what size tire? Can you also tell me why this set-up works?
If you use the 18"/17" combo you can't get many real slicks in 17". All there is are DOT race rubber like Hoosier Aso4 and Kumhos etc... So with the limited 17" slick sizes what combo here works. I love slicks but they are always higher profile than DOT race rubber. They use differnent sizing. Pirelli uses overall diameter so that several differnet widths are all the same diameter such as 305 645 18 (645 is the diameter), goodyear 25.5 11.5 18 = 25.5" diameter 11.5" tread for 18" wheel.
Part two: If you use a second set of rear stock oem's on the front and then stock rear 18's on the back what is the best tire combo for that compromise? 305 front with 315 rear?
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