Chair tires

[Michael Vinten]

Does anyone know of a supplier for the tires used on the chair? I believe they are 145 x 10, but can't confirm as my rig is not here. Dunlop does not appear to carry them. Are radials or bias preferred assuming there is a choice?

[bfd]

Michael
I got mine here:
http://www.minimania.com/web/item/FALKE ... Detail.cfm
mine was a different brand but the same idea. It has multiple seasons on it and is still going strong

[limy_1]

I know that some have the 8" trailer tire.
The benefit to that is you can get a replacement almost anywhere at anytime even if it is off your trailer

[Stephen Szikora]

How is this tire legal when the rules specify maximum 125mm section width for P2?

I note that the term "section width" can be confusing because a 145/80-10 tire such as the Falken has a 145mm section width (5.80" when the rule states 5.00".) Meanwhile, a Dunlop R2 sidecar tire at 3.50-16 has a section width of 107mm (while 3.50 corresponds with 87mm, which is the tread width.)

To visualize what a legal tire would be, a 4.80-8 Carlisle Sport Trail trailer tire has a section width of 4.80", suitable for P1 and just under the 5.00" rule limit for P2. However, a 4.80-8 Carlisle USA Trail trailer tire (another model in their line-up but with a different carcass) has a section width of 5.10" which is over the rule limit for both P1 and P2 even though it is the same nominal size. Now, imagine the skinniest trailer tire you can get from Canadian Tire beside a Mini tire. Clearly the Mini tire is too wide by our rules.

I'm not protesting, just want clarification. I have in mind a 120mm tire that has a section width over the limit and I'm wondering if it can be used. Do we care about how much the sidewalls bulge or do we really just care about the tread width? If it is the latter, then perhaps the rules should state "tread width" instead of "section width". Regardless, Mini tires don't fit either way.

[paul whittaker]

The std trailer tires are not meant for race speeds. I have seen Inky dump a whole wheel and tire in the trash can which started off new that day. So for safety reason alone a better ire has to be available, since no one make a race tire (that I am aware of) to fit our rules, what is the option? Second My 1969 rig used Centurado tires this size all round, so consider it historic practice. All the center bulge does is rub on the frame, not a competitive advantage IMO Paul.

[Stephen Szikora]

Again, not complaining, just clarifying. It sound like a rule change is in order. Of course, the obvious solution is to use "big wheels" and put the Dunlop R2 on the chair as well. Maybe a distinction ought to be made between P1 and P2 in this regard.

I just checked the USCRA rules and noted the following: they are the same as the VRRA rules for P1, but for P2 (Super Vintage in the USCRA) they do not use the term "section width" but instead use the term "footprint width" (but in the same dimensions as the VRRA.) "Footprint width" is not a tire industry term but must refer to "tread width".

May I suggest the following change and that it be coordinated with the USCRA: tire size rule to read "125mm tread width front and rear, and 145mm tread width on chair." This would work for the P2/Super Vintage rigs. A separate decision can be made for P1/Classic rigs as to whether or not you want the wider chair tires. It might make sense to restrict them to the big wheels to distinguish them but I don't know if there are current rigs that would not fit that description.

[chairman]

chair tyre size and type has as a rule of thumb, has been left to the the personal preference of the driver.I have used bias and radial types but dont have a preference. the setup for each type is different.the high speed trailer wheel works best with the spindle angled up to tilt the wheel in at the top. this gives good tyre wear and resists the rolling under that shreds bias ply tyres. as we know wheel and tyre sizes expanded in the late sixtys. our rules allow playing in certain parameters to keep the playing field even and cost down. I do see shortly rumblings of wider rear tyres and mag wheels in the not so distant future. ever heard a chair tyre howl as it rolls under ?

[Stephen Szikora]

Consider the following: If the rule was tread width and not section width, it would be possible to use vintage racing treaded Formula Vee front tires, for example the Dunlop CR82. Their nominal size is 120/590-15. 15 rims are already allowed in P2. The challenge then is an appropriate wheel. It is possible to purchase 15" aluminum hoops designed for mounting car tires (specific bead) and in appropriate widths. A FV tire is supposed to mount to a min. 4" wide rim. These are available for bikes in aluminum and come un-drilled, to be drilled and laced to any hub - the custom guys use them. Also note that vintage FV racing tires are available from both Dunlop and Hoosier.

As currently written, these tires would be legal for the USCRA but not the VRRA because they use the term "footprint width" (a proxy for "tread width") and we use the term "section width". I'd imagine these tires would perform very well and last a long time on a sidecar. They would be wider where the rubber meets the road than the Dunlop R2 (tread width of only 85mm), but the R2 is already under sized by the rules. It is used primarily because it is the only game in town.

Dunlop also has a vintage Mini racing tire suitable for the chair wheel, the CR65 in nominal size 5.00L-10. It has a tread width of 120mm like the FV tires. The issue for all these Dunlops is that both the bike tires and the chair tire have a "section width" of just over 160mm. The are classic bias-ply racing tires with the associated rounded sidewall profile. Again, under VRRA rules, these tires these would not be allowed but under USCRA rules they all would just because of the difference in wording.

A few specs to consider:
Dunlop R2 - 107mm section, 85mm tread, 618mm diameter, 4.0kg weight, 2.63" rim width.
Dunlop CR82 - 161mm section, 120mm tread, 579 mm diameter, 3.8kg weight, 4" rim width min.
Dunlop CR65 - 165mm section, 120mm tread, 498mm diameter, weight unknown, 3.5" rim width min.
Hoosier FV - 152mm section, 120mm tread, 565mm diameter, 4.5kg weight, 4" rim min.

Here's an interesting thought for the USCRA - what's the "footprint width" of a regular rounded motorcycle tire? We should both be using either "section width" or "tread width", and understand that the choice of which one to use makes a big difference in the eligible tires.

[paul whittaker]

tread width for solo tires is almost irrelevant since the profile has as much read on the sidewalls as on the footprint. Footprint is very relevant for cars and sidecars which do not lean. availability is a major concern, followed by price. Both come after does it work? Paul.

[Stephen Szikora]

Let's be clear ... I'm not advocating for wider tires. Just noting a disconnect in the VRRA/USCRA rules.

I got to this point because once again, I dusted off the plans set I got from you, Paul, and started looking around the garage at the bits I've accumulated. I knew the P2 rules specified min. 15" wheels and I thought the stack of CSR rims were 15". Then I noticed online the discussion of 3.50-16 R2's and realized that the tires were only available in 16". So, back to the garage to confirm that, indeed, the CSR rims are 16". Curious to know if this was the only option, I first checked the rules to know what to look for. That's when I noticed the disconnect between the VRRA and USCRA rules. I verified my understanding of the difference between tread width and section width and voila - a problem apparently exists.

I also have a keen interest in vintage car racing and knowing that the FV fronts are relatively skinny and 15" diameter, checked the manufacturer documents to find out their detailed sizes. That's when I realized they might be usable on a sidecar, but because of the very slight difference in rules they would be OK in the USCRA and not in the VRRA. So, I raised this point of clarification to educate everyone to the problem and the possibilities - not on its own, but because I saw that there was a discussion on chair tires and having just read the rules I also realized that the tire in question wasn't kosher.

To your key points, Paul, availability of FV tires isn't the issue that the R2's seem to be (from other posts.) Not exactly off the Canadian Tire shelf, but available from suppliers. There is, however, no significant cost savings - the Hoosiers, for example, go for $200 each. Also, as you astutely point out, they will rub on the swingarms of existing rigs because of the wider sidewalls. Anyone wanting to run these tires would have to build a rig to accommodate them.

So, certainly the rules ought to be corrected to reflect the intent of the powers that be, and they most definitely should be adjusted to be consistent between the clubs.

My personal opinion is worth squat but I think it would be nice to see P1 rigs on the R2's and let the P2's get more creative (as is apparently historically correct.) The 16" wheel rule for P1 sort of dictates this result. I should also point out that I got started on this when looking at pictures of classic and post-classic rigs from the UK and wondering what tires they were running. It seemed that many that would be contemporary with our P2 were running wider tires than the R2's (though I love the look of the big wheelers by contrast!)

If people want status quo, all they have to do is change the P1 and P2 rules to allow for a wider section width chair wheel. The more limited section width will force use of 16" wheels and R2's. Just hope no one from the USCRA reads these posts and shows up at Mosport wanting to run the rig I envision and allowed by their rules!

[paul whittaker]

There have been conversions to 15" (I believe just on the rear) Andrew Fairbank certainly did one in USCRA and Peter McKinstry seemed very keen on it. I did recommend a 15" with VW tire for the P2/3 of Clark Wallace since he experienced traction problems with the GT750. IMO if you cannot break traction with the 350 snows, I see little advantage to all the effort going into the conversion. And I doubt you would ever need a wider tire on the front of a P1/2. Honda used a 15" spoke on some Gold Wings, but not much wider. The CSR/LTD 48 spoke wheel are good due to the extra side load strength of 8 more spokes, and they come with alloy rims ready to go. Rules generally suffer from solo experience; you can enter a shop and buy a brand name off the floor, so the rules are written to reflect general availability, with mods allowed or not. Sidecars have always been and still are constructed from whatever seems to work, from bikes, cars, outboards etc, and road race versions were never available from the dealer. I do realize that there has to be rules and the onus is on those that race sidecars to clarify them. It just never cropped up until now. Who cares how wide the tire is, the tread on the pavement is what matters. Paul.

[Paul&Sharon Bowyer]

My period one original Feddaman chassis uses and always has used a 10" mini wheel. I forget the section width but will look at it this weekend.
Paul

[tintop]

I had the same question regarding the wording of the P2 sidecar rules -

My question to Rick Yates & his response:

"...In the P2 section it gives a maximum tire width of 5". Is this tread width? Dunlop offer an 'L' section vintage racing tire in 4.7" & 5" tread widths, could I use these?"

"Yes the 5" is the maximum"

Excel make a 5.5 x 15 alloy rim, and Dunlop make Formula Junior tire(s) with classic C65 tread pattern, as noted in my inquiry to Rick. These should work well on a sidecar, as they are designed to slide. However, I consider 48 spokes insufficent for the side loads a sidecar can produce with that much tread, and rim width. 60 would be a minimum, 72 the best, unfortunately there is not a suitable hub available that meets that criteria. One possibility I looked into was having Central Wheel make up some hubs using two inners from the MGA (60 spoke), or an MGB (72). They can also supply a suitable alloy rim.

Brian

[chairman]

if one was to observe, a rig with 15 inch wheels with the mentioned rubber was running at mosport this past season. why are we reinventing the wheel. build your outfit and try to make it handle. the tyre issue will be a minor one. dont stick handle yourself into a corner and dont think car, this is not a two wheeler or a four wheeler so ditch those two.

[tintop]

Sidecars have historically been a mix of both motorcycle and car technology, since the evolution of the 'kneeler'. The issue isn't whether suitable tires exist that comply with the rules, clearly they do. The issue is sourcing a spoked hub that will be both safe & reliable. As has been pointed out, 10" (& 13") rims were definitely in use during our P2 period. There are many period photos to support this.

The reality is that the current P2 class is really P1's with 750cc engines. The restriction to twins in P2 ignores the historic fact that multi's were running then. Both the Trident, and Honda 4's were in use.

The engine sizes of P1 & P2 as Vintage (650) & Super Vintage (750) is not the issue, the 15" wheel in P2 is. It would seem to me that there should a P3/A & P3/B (Classic & Super Classic??) with a 750cc (4 stroke) engine size for P3/A, and 900cc for P3/B. Both allowed 10" or 13" wheels with P3/A restricted to treaded. My .02