Discs AGAIN

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Dietmar
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Discs AGAIN

Post by Dietmar »

SCCA is considering allowing 4 bolt wheels. This would allow for aftermarket discs.
If you have an opinion one way or another, now is the time to voice that opinion

Borrowed ( stolen) from that "other" site.
FV
1. #28955 (Formula/Sports Racing Committee) Allow 4-bolt pattern wheels from 1967-1973 Type 1
In GCR section 9.1.1.C.3.C, make changes as follows:
"Wheels shall be standard fifteen (15) inch X 4J as used on the 1200cc and 1300cc VW sedan as defined herein or 1967-1973 Type 1, or any steel fifteen (15) inch X 4.5J VW wheel with the same 5-bolt pattern as the standard fifteen (15) inch X 4J wheel or 4-bolt pattern of the 1967-1973 Type 1, all within the track dimensions of C.2. Wheels may be balanced only by the use of standard automotive balance weights (adhesive or clip on). Hub cap clips shall be removed."

Dietmar
(text should read 68 Type 1, not 67)
BLS
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Re: Discs AGAIN

Post by BLS »

Hi Dietmar,
Just so it's clear, this allows us to use an aftermarket disc brake kit designed for 4 bolt VW wheels which are commonly available and at reasonable prices. Is that correct?

Thanks,
Barry
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Re: Discs AGAIN

Post by BLS »

And while we're here :)

What is the definition of "track"? How is that measured? Centerline of tire? Outside to outside?

I make the assumption the value of 4 bolt wheels is the availability of link pin disc kits that convert the wheel to 4 bolt and keep the correct track. Otherwise I don't see the value.

None of the kits actually state what the track width will be or if it is maintained. At least not the ones I see.
Barry
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Re: Discs AGAIN

Post by BLS »

I went out and measured my front "track". The maximum is 52.5 which I cannot reproduce at all.

The data I find states the standard track as 51.5, which is close to my centerline. I don't know if it is aligned properly at the moment and I'm measuring across the top so neg camber will bring it in a bit.

But the track must be center of the tires as I can't get close otherwise.

So, is the 52.5 max allowing for something? Like 4.5" width wheels rather than the original 4"?
Barry
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Re: Discs AGAIN

Post by hardingfv32 »

Yes, but the 4.5" wheels only add .5" total to the front track.

Brian
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Re: Discs AGAIN

Post by BLS »

Hello Brian,

OK, I see that with the backspacing. How do you get to 52.5?

With the 4.5 wheels are we at 52 then?

And, is the track the centerline of the tires? or measured elsewhere? Center of the wheels? Mounting face of the wheel?

Thanks,
Barry
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Re: Discs AGAIN

Post by FV80 »

From the SCCA GCR - Appendix F. Technical Glossary

Track – The distance between the center of the rims of two wheels at one end of a car, with any angular
adjustments at normal settings and steered wheels in the straight ahead position.

It is INTERESTING that it does NOT address toe-in, or camber.. I guess that would mean 'at the 'rotational center' of the wheel? .. which should negate the other considerations.. just pretty much IMPOSSIBLE to measure specifically at that point ... [follow up .. I also guess that the definition defines the 'center of the wheel' as the IMAGINARY CENTER of the wheel .. since there is NOTHING at the actual CENTER of the FV wheel... either 5 bolt or 4 bolt! The 'center' would be buried down inside the BRAKE DRUM .. (or ROTOR.. as the case may be). ]

[SECOND FOLLOW UP - From my observation, I have seen tech people check the track by measuring from the inside of one wheel to the outside of the other side. Poor at best, but I'm assuming they are really just checking to see if the car track is "in the neighborhood". They do it WAY too fast to be really accurate at it .. and I haven't seen them paying any really attention to how "facing straight ahead" the wheels really are. ]

What a TANGLED WEB WE WEAVE :mrgreen: :mrgreen:

As for the kits .. SCCA holds the DRIVER responsible for ensuring a 'meeting of the rules'. The KIT sellers are NOT concerned with our rules. It is up to each purchaser to investigate and make his/her own decision. The MFR/Dealer may SAY things like "no track change with this kit", but HE is NOT responsible if there really IS a change .. YOU ARE. Although I THOUGHT the 4 bolt wheels were only available in 4.5" width, I have seen some indications that there might also be some 4" wheels too.

Regardless, the SCCA **PROPOSED"" new wording (it's NOT YET A NEW RULE as far as I know .. just under consideration - they are ASKING FOR MEMBER INPUT) is written to say that the 4 bolt wheels would be ALLOWED, but all other rule limitations (TRACK!) remain in place as they have been for a number of years.

Steve, FV80
The Racer's Wedge and now a Vortech, FV80
To sign up in the FV Registry for updates about SCCA Formula Vee, please send me an email or PM with your name, location (city/state), make/model of car, phone # and any other appropriate info.
BLS
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Re: Discs AGAIN

Post by BLS »

Hey, thanks Steve.
I was thinking yesterday that there was a definitions section in the GCR but never did remember to go look it up.
Pretty hard to measure to the wheel centerline with tires mounted I would think unless you are certain the tires are symmetrical to the wheel, and even then how do you define the tire edge to get a center of the tire?
Measuring mine to some old scribed marks that were near the center got me close to the standard track so it seemed to make some sense.

I'll just have to wait and see if this goes through. I'd like to finally finish the car before I get too old to drive it :) and I need the extra space disc brake pedal position can provide.
Barry
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Re: Discs AGAIN

Post by hardingfv32 »

1) I cannot measure right now, but when using 4.5" wheels I have always been very close to the max track. Never any thought about how to get out to the limit.

2) GCR Appendix G does a very good job specifying how to measure track.

Brian
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Re: Discs AGAIN

Post by BLS »

Brian,

I just read it and it does describe it well. Thanks for pointing it out.

Just looking, some 4x130 disc kits for link pins indicate they will increase the track by 1". It's not clear if they mean 1" per side or total. I'm not sure it solves anything unless there are near stock track kits available. I do find at least one 5x205 that is "zero offset". Not sure why that wouldn't work since we have an extra inch to work with.
Barry
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Re: Discs AGAIN

Post by hardingfv32 »

I am pretty sure Andy Pastore had something figured out for the front using 4 bolt wheels. He had a request in to the CRB to allow 4 bolt wheels. Search Apex Speed.

The main issue is that there is nothing available for the rear that meets the rear track spec.

Brian
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Re: Discs AGAIN

Post by BLS »

If you can't make it work for the rear, not to mention the front, does anyone know the value of the 4x130 wheels?

Without having parts in hand it's impossible to know what track you end up with. You would think the kit sellers would know and publish the track. Street cars with fenders have an issue as well.
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Re: Discs AGAIN

Post by BLS »

OK, I waded back into the disc brake thread at that "other site" :)

Andy Pastore used the 4 bolt wheels, front only, and off the shelf VW parts. The track width is within spec because the 4 bolt wheel offset pulls it back in.

Andy kept the standard drums on the rear.

The real downside seems to be the weight of the 4 bolt wheels.
Barry
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Re: Discs AGAIN

Post by hardingfv32 »

BLS wrote: August 6th, 2020, 11:18 amThe real downside seems to be the weight of the 4 bolt wheels.
Now you are just regurgitating truisms. While lighter wheels are in fact a benefit, it is not something that you will be able to measure on the clock or with a data system. This is something that only people in F1, etc. are capable of evaluating. You are talking very small values.

Stay on task!

You said the goal was a shorter pedal travel. The fact is you are talking about a .5" decrease in pedal travel by changing to discs. I am assuming a optimized and properly maintained drum system. So does .5" solve your packaging issues?

Brian
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Re: Discs AGAIN

Post by BLS »

Yes, it helps. I went to a lot of trouble to lengthen my chassis 2 inches in the front (Citation, which has a 81.5" wheelbase), and change the brake system to front mount masters, and change the steering to allow for left foot braking. All that and then I've been unable to get back on the track due to work issues. And I'm not getting any younger. At 6'4" I'm not the poster boy for FV drivers. Back in my 20's I managed it just fine. Stupid kid didn't know being cramped up was bad.

I think 0.5" is on the low side. I believe I can get closer to an inch. And an inch is bigger than it sounds. I will have discs, at least on the front. I could live with drums in the rear I think, depending on the brake pedal travel. I would just like to keep the cost reasonable.
Barry
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Re: Discs AGAIN

Post by BLS »

"Stay on task!"

Good point. The weight is probably not something I will notice. I suppose it depends upon the weight location. If it is outer it might be a problem, but Andy's report indicates not so much. I do know that back in the old days when rain tires were heavier than slicks, it made one hell of a difference in accel and decel.
Barry
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