You are correct, the shocks would need to be re-valved. The lower mounting point creates a motion ratio close to 1:1, where it is currently .5:1 with a LP assembly.
This thread is an eye opener. A lot more work to convert than I thought. If there is a weight penalty, then I do see myself making such a conversion.
Brian
Steve,
I guess if you have droop limiting shocks there would have to be some change or maybe you can get the length of the modified shock tower set close enough. Depending on the angle of the shock the motion might not be what it appears at first glance. Something to ponder anyway.
Brian,
Yes, it's not that simple. Would it be better? I'm not so sure. I'm not against it as an option.
Thanks,
Barry
Last edited by BLS; 09.11.13 at 11:22 AM. Reason: See Brian's comment
What would have been better imho is allowing a conversion kit for our current beams.
Unfortunately, it turned into a beam, wheel, tie rod, shock conversion package. NFW am I doing that. All I wanted was to be able to run discs so that they never had to be adjusted, had a large selection of cheap pad compounds, and could be inspected in under a minute. Too bad the committee twisted my request. I would have rather had them have said "no" than go off on full wheel to wheel beam redesign for FV.
I am still at a loss on why a spec conversion kit for our current beams is a bad idea, but I have a feeling I will never get an answer to that one that satisfies me.
Oh well, see you in the spring on my hoarded carbotech shoes and could crack anytime drums.
Craig
If you are prepared to design, build, market, and distribute such a kit, I am sure there would be support. There is not such a kit on the market. Kits, that may appear to do that, have more negatives than positives, and are very expensive.Originally Posted by craigs
Greg Rice, RICERACEPREP.com
F1600 Arrive-N-Drive for FRP and SCCA, FC SCCA also. Including Runoffs
2020 & 2022 F1600 Champion, 2020 SCCA FF Champion, 2021 SCCA FC Champion,
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We are currently looking at options for making a simple disc conversion using the standard LP beam. Some of what we are considering is finding a way to use the turkey legs and parts outward of the beam from the BJ beam with the actual LP beam. That would basically eliminate the need and hassles for switching beams yet still allow things like the FST brake package. The issue right now is the lower turkey leg where it goes into the beam. I think. We are open to making and selling what ever adapters / pieces might be needed for such a conversion. This is very early in the thinking process however.
I'm hoping to have more information soon and be able to have several options to explore. I've been a bit busy with that crazy september race thing to spend too much time on this yet.
What's going on in September?
Reinventing the world, one wheel at a time.
A small race for a dying class only 50 entrants ;-)
Mark Filip
How would this be possible with the different center to center locations of the link pins/ball joints on the respective uprights?
Brian
Is braking performance limited to the grip level of the front tires on a FV? Does the type of brake system, drum or disc, make any difference?
I assume it does not. If so, then why not a more open rule that allows for a five-wide after market conversion or BJ assembly? Add the weight penalty to cover any possible performance improvement and require everything to be steel. Also leave open the possible use of drums in the rear.
Personally, I feel the five-wide conversion is much more economical when everything is taken into consideration.
Brian
yup..
Possibly less pedal effort required for the same amount of braking, so potentially easier to modulate and stay at peak braking with disc brakes.. Maybe.. Sort of the same advantage as carbotechs at most tracks where even stock shoes wouldn't fade, but require a lot more effort on the pedal, hence harder to hit the same amount of braking consistently.
I think it could work, but caster would change with suspension travel, assuming all the joints would stay in the same spot.. Haven't thought about what that would actually affect. I'd have to sketch it to measure if the change would be significant or not.
Mike mentioned adapters, so maybe he's thinking about relocating the ball joints? I'm interested in seeing the outcome of this, either way
My experience running with FST's is that tire grip rules. Back when they were running real R60's I ran with them at RA. I could outbrake them and make up a a fair bit of what I'd lost out of the corners. Just this August I ran with them again. They are now running R55A's since Hoosier does not make R60's anymore. Running R55A's myself (three year old ones...) I'd judge the braking as essentially equal. With the top couple drivers I ran with there was no discernible difference. I could complete an outbraking maneuver if I had a run and they could do the same to me.
Some have said that brake modulation is inherently better with discs. This may true in their experience with other vehicles, but I do not believe this is true for the drum brakes on a Vee. Most older, especially American car, drum brakes are "self energizing". They were designed this way intentionally to decrease pedal effort, especially before power brakes were common. What this does is make the torque applied to the shoes by the drum, push the shoes harder into the drums. This could definitely make the brakes less easy to modulate because to reduce brake effect you'd have to reduce the pedal pressure more what is needed to increase it: a non-proportional brake response.
VW drum brakes are not a self energizing design and therefore provide a reasonably proportional response relative to and increase or decrease in pedal pressure making them relatively easy to modulate.
Developing a disc brake option for the 5-wide wheels is a fundamentally difficult design challenge. You need one relatively large, stiff and very strong "flanged hub" to which to attach the wheel. It needs to be as stiff as and support the wheel just as far out from the center as a current drum does. Otherwise, the wheel will flex even more than it does today. You need a second "large flange" attached to the hub inboard of the wheel flange: the disc. There is no way around this. It WILL be heavy or it WILL be expensive (or both). We (the committee) looked at commercially available conversions back in 2005 and they were all very heavy. Did Porsche stay with 5-wide wheels when they went to discs on 356's. No they did not and for good reason.
Designing a custom 5 wide disc system that is FF like would be a wonderful exercise. It would be expensive. And would it really fit the philosophy of FV?
Just a couple of years ago Steve Davis tried a 4 bolt disc kit for link pin beams with 4 bolt VW wheels. It was a pretty simple bolt on and worked, though he could only run it for one session (not in the official SCCA event). It was heavier than the drum set-up especially including the wheels. But it did bolt on and it did work. But it would require 4 bolt wheels.
Those that think going to a BJ beam would newly create a "FrankenVee" should take off their 66-67 slotted wheels and wide rear drums (from ball joint equipped cars...), and their 1600 engine cases and their 1.1 rockers, etc. etc. Yes this is a bigger change, but it is not really that different philosophically. Using BJ parts on a LP beam has some merit but is going to require special made or modified parts which simply will not be cheap.
The BJ spindles are way better than the LP ones and yes I know, you can (should) run preloaded spacers between the inner races as I have done since I started in FV in 1995. But many don't and spindles continue to break.
The committee was not looking for a way to make a Vee faster, just more reliable and over the long run, maybe cheaper to operate. Difficult to find, $200 per axle drum shoes is not helping the class. We also feel strongly that IF we are to go to disc brakes we should not start a "third way" but should use the experience gained in FST to our advantage.
With the proposed 25# weight penalty and 4 bolt steel wheels I can just about guarantee that the current drum configuration will still be the "hot" set-up. But we believe the proposal we are making (at the request of the SCCA FSRC I might add) is overall the best option to allow those that really want to run discs to have a way to do so. As these early adapters learn and show what's possible, we can adapt and adjust the weight penalty.
BTW, the proposal as written will allow you to put discs on the rear OR retain the 5 bolt rear drums as is OR move to 4 bolt rear drums.
Bruce
Last edited by Bruce Livermore; 09.13.13 at 12:31 AM. Reason: Typos and a bit of clarifying...
Are the track measurements in the same range?
Brian
I find the front track on a 73 Karmann Ghia with discs, ball joint beam, 4.5J x 15 wheels is listed at from 51.3" to 51.7" (different sources). FV spec is 52.5" max. which was increased a few years ago to allow the 4.5x15 wheels when the suppliers told us there were no more 4x15's available. So there should be no problem there.
Rear track is harder to figure since there was never a VW made (that I know of) that had short axles and 4 bolt discs or drums. All of the 4 bolt rear drum Type One's including Ghias were '68 and later so had the long axles. The rear track on a "73 (which of course is not a swing axle) is listed as 52.7" or 53" from those same sources. I cannot find a spec for a '68 or '69 Ghia which had the long swing axle. But I did find a '68 or '69 Type 1 owners manual that lists the front track as 51.6" and the rear track as 53.3". This is of course outside the FV limit of 50.75". But none of this really matters since we (and FST) use the short axles...
My best guess is that the rear track with short axles and the disc brake kits will be within or very close to the 50.75". I base this on the FST specs which list 57" max track at the front and 55" max track at the rear. Assuming the same wheels all around, that would put the rear track with stock 4 bolt wheels at about 50" or about the same as a FV with 4 x 15 wheels.
Bruce
I know believe the Ball joint beam is the wrong way to go for FV for sure. I just spent some time looking at my Womer which might be one of the easiest car to convert to a BJ beam as my steering box would not have to be touched because its not on the beam and I will say I would still not do it. In order to do it correctly it would take more time than I think it would be worth, yes I could bitch it up and bolt it on but I refuse to do that. I have also looked at a Caracal, Citation, Mysterian and a Protofrom P2 all cars would be way more work "to do it correctly" without hacking up the cars.
If disc brakes are a must for some I would rather see a wide 5 conversion be allowed there are tons of kits already out there, unfortunately some are really cheaply made for around $300-$400 for the front and there are some very nice kits that may be more suitable to be on a race car for $800-$900. This cost much less than to convert to a BJ beam ($1400) and way less time to put on then you still need 4 bolt wheels. Wide 5 kits would Keep same wheels same steering box location and you don't have to touch the body or mess with the track or shock valving not to mention you won't have to run those ugly 4 bolt wheels that look like the will flex more than the tires.
Mark Filip
http://www.porterfield-brakes.com/Difficult to find, $200 per axle drum shoes is not helping the class
$119 a set
In my experience work as good if not better than the Crabotechs and so far seem to be much easier on drums.
Mark Filip
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