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P2 15" tire rule change proposal

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P2 15" tire rule change proposal

Postby johnw » Thu Aug 01, 2019 2:59 pm

Hey gang,

I have submitted a rule change proposal and wanted to post the synopsis of it here, as I am looking for support this fall in order to get our rules in line with USCRA and AHRMA:

Here is the background:
P2 sidecar rigs are allowed 15" minimum diameter tires. There is a limited selection of tires to choose from in this size, and only one is actual racing compound. Here are basically the two: Firestone car tires (for street going dune buggies, DOT) or Hoosier racing tires (I think from Formula V racing, sticky). Hoosier tires are allowed in both USCRA and AHRMA, while not being legal in VRRA.

Basically, both AHRMA and USCRA have a rule for P2 sidecar tires that allow for a 5.0" tire contact patch on the sidecar front and rear wheels. In a strange contrast, VRRA has a rule that says 5.0" maximum section width.

I propose we should change the rule to say 'contact patch' instead of 'cross section'.

As any car racer knows, unlike a solo machine, sidecars can only use the rubber that is contacting the track, so fatter sections are of no advantage. You could have a 10" section width tire, but if only 5" was contacting the road, it acts the same as a 5" section tire with 5" contact patch. All that matters is the contact patch. ie: what wet mark is left after you drive through a puddle.

The rules from all 3 clubs:

Here is the existing VRRA rule:

10f. TIRES: maximum 125mm/5.00 inch section width on front, rear, and sidecar. No slicks or slicks
treaded after manufacture.

Here is the AHRMA rule: WHEELS & TIRES: Front and rear wheels must be of wire-spoke construction; sidecar wheel may be of solid construction. No slicks or hand-cut tires. Wheels are to be minimum 15” (381mm) diameter front and rear, and minimum 8” (203mm) diameter on the sidecar. Tires’ contact patch, measured with race-ready air pressures and fuel load, with driver and passenger on board are to be a maximum 5.0” (127mm) width on front, rear and sidecar.

From section 6.2 in USCRA rules:

4. Wheel and tire sizes: Minimum 15-inch diameter on front and rear,
minimum 8-inch diameter on sidecar. Tires: maximum 125mm / 5.00”
footprint width on front, rear, and sidecar.


John W
Posts: 42
Joined: Sun May 09, 2004 8:05 pm

Re: P2 15" tire rule change proposal

Postby MGill » Mon Aug 05, 2019 11:33 pm

Thanks for putting this together John.
VRRA Member
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Joined: Sat Aug 11, 2007 7:41 am
Location: Sarnia,ON

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