L/w Uprights...

[Guest ScotMac]

Hi all,

 

First of all, i believe the wishbones on the lightweight are pretty much the same the ones on the 2b-plus/superspec, so this question is fairly generic...can someone confirm this (that they are the same)??

 

I have a set of sierra/xr4ti brake/hub assemblies, but i want to switch to a MUCH lighter more performant solution. eg, something like (capri upright and brake):

 

http://www.stuart-taylor.co.uk/images/products/003.jpg

 

The question is "what upright/hub/brake assembly can be used w/ the wishbones?? Just sierra? Cortina? Capri? ????"

 

I have heard that the sierra uprights have geometry problems, and it is better to go w/ the coritina uprights (this info was from MNR's marc norton, who *PRODUCES* a performant version of the sierra upright!!!).

 

Thanks, -sm

[Guest rizla]

what marc says is true about the sierra hubs,but only if they are unmatched,ie different casting numbers

 

the lightweight at one of the shows had some custom ally jobs that looked good

 

but id still go for the sierra hubs,the weight saving isnt that drastic

 

and the best performance part in a lightweight will be a personal diet ie slim fast

 

im 17stone,drive a car thats 420kg and it still goes well so unless your competing in the rgb save your money

[Guest ScotMac]

The problem w/ the sierra geometry, as i understand it is that they have too much kpi...ie, the top is way to far inboard, causing problems w/ scrub. You can actually see this fairly clearly by just looking at any of the closeup pictures of the 2b or superspec. eg, take the following image, and zoom in on one side of the car...the fairly extreme inboard angle of the hub is obvious :

 

http://www.robinhoodsportscars.com/kitrang...ages/2b/2b1.jpg

 

Also, the sierra front hubs and brake assemblies add around 80 pounds (2 sides combined) to the weight of the car. For a under 1000lb car, that is NOT trivial, ESPECIALLY considering that much of that weight is unsprung weight!!!

 

Note, in terms of the slim-fast, that is about half of my weight!!!

 

Anyway, that is all good background info on why i am asking the question, but still doesn't answer my base question....what can it be switched to???

 

So, i would need to somehow modify the top wishbone, or extend the ball joint bolt? ie, tt would need to be longer, obviously, for the "better kpi" upright ?

[Guest Battery Bill]

Scot

That picture is not really a good example to use as it looks like the front wishbones are at far too steep an angle.

 

You should chat with Richard Hall who now works for Robin Hood, he is quite a wizz on the geometry thing, he has made some longer and different angled "Dummy Mcpherson struts" which he says make a whole load of difference, and he was pretty quick round Donington this year in his 2B

[Guest ScotMac]

Thanks Bill. Getting in touch w/ anyone w/ technical knowledge at RH (especially Richard) seems to fairly difficult (and is compounded by the time difference).

 

I understand that the car in the picture may be showing an extreme version of the problem. However, my understanding is that the kpi problem is an inherent geometry problem w/ the sierra hub, that all installations will have in varying degrees (w/out substantial modification to the hubs).

 

I also understand what you are saying. ie, the shocks in the picture could be adjusted to allow the wishbones to be at a straighter angle from the car. Then the top wishbone could be adjusted "out" to fix the camber that got screwed by adjusting the shock. This would then obviously have a positive effect on the kpi problem. However, there is an limit on how much can be done, in this manner. ie, you will eventually run out of shock adjustment, and ride height (the above adjustments lower the car).

 

Anyway, i would want to make the switch, just for the weight savings. If i can clean up the kpi at the same time, all the better.

 

So, any good alternative uprights/hubs?????

 

Thanks again.

 

-sm

[Guest rizla]

i must be missing a few marbles .......so you say a sierra hub (1)wieghs aprox 20kg

 

ill be amazed if thats true,as the total you quoted for 2 of them is more than the weight of my chassis,or nearly that of my engine and gearbox added together

[Guest ScotMac]

It's true. And now u understand my point!!!

 

BTW, not the hub. I said the hubs and brakes. Note, that is for a 10 1/4 inch front rotor. I have weighed them *3* times now. The hub and upright weighs about 13lbs, the rotor and caliper weighs about 23lbs. So, that is 36, minus all the fittings (nuts and bolts, etc). So, atleast 38lbs. BTW, that is NOT 20kg. 40/38lbs == 18/17kg.

[Guest ScotMac]

BTW, again to remind everyone, the question is NOT about the weight, NOR the kpi. The question is, what alternative uprights/geometry can be used (cortina, capri, ...)?

[Guest docter fox]

either I should be asleep by now or I'm getting confused with the translation, I'm guessing a rotor is a disk? perfomant is performance and kpi is another word for camber?

 

1kg of nuts for holding the calipers on and 17kg of caliper and hub assembly, I must be stronger than I thought

 

wouldnt giving less negative camber actually raise the car? as i was wanting to lower mine but thought I would end up with to much negative camber and have to play with the coilovers

 

I would try Richard Hall, he's a different Richard to the one I think your thinking of

 

It's been a long weekend so sorry if I'm rambling

[Longboarder]

KPI is king pin inclination and the sierra hub carrier is a major compromise because its designed to work with a MacPherson strut putting the upper joint too far inboard. Machining new mushrooms reduces it but a early cortina or possibly escort hub carrier is inherantly better suited to double wishbone conversion or you could try Raceleda who make a cast alloy hub specificaly for this job.

 

Nigel

[Guest ScotMac]

Yes, rotor is disc. Performant is adjective form of performance (common in computer circles...yes, i am a geek). You brits need to work on that english thing!!

 

No, KPI is NOT camber. KPI is KingPin Inclination or "steering axis inclination" . Here is a good description of suspension terms:

 

http://www.roversd1.nl/sd1web/suspension.html

 

So, Bill mentioned that the wishbones were too steep an angle (which in fact was caused by the KPI problem!!!). I thus replied that, yes, the angle could be reduced by adjusting the coilover, and then by removing the resultant *negative* camber by adjusting the wishbone (unscrewing the top ball joint from the wishbone a bit). ie, those two adjustments could *REDUCE* the *KPI*. However, i noted that there is a limit to those adjustments, and they could have *other* negative affects.

 

EDITED: Note, the above will reduce the wishbone angle, but will not affect the KPI. The KPI is a fixed attribute of the hub...no way of helping it.

 

Regardless of what Richard is meant, I have stayed up till 2am PST *3* times, and have yet to be able to talk to a technical RH representative.

 

In terms of the weight, ignore the 2 pounds i added for the fact that the hubs and brakes are not actually mounted (nuts and bolts, *etc*). THE 36LBS IS STILL WAY TOO HEAVY!!!!! :angry:

 

And, YES, the hubs and brakes (including rotors) DEFINITELY DO WEIGH 36lbs...atleast the ones sitting in my garage do!!!! YMMV.

 

Rather than negatively questioning the premise (which *IS* *VALID*), does anyone have a positive response to whether the hubs and brakes can be swapped for a nice capri (or cortina) upright and brake assembly like the one i listed in the initial post.

[Guest ScotMac]

Thanks Nigel, finally a positive response.

 

Yes, i have seen the racelada stuff quoted. Will it *easily* hook up to our (2b, superspec, l/w) wishbones? ie, w/out much/any fabrication.

 

BTW, the reason i mention the capri/cortina uprights, is that i believe that one of them can be combined w/ racelada stuff to substantially reduce the price...any thoughts?

[Guest ScotMac]

By combine the capri or cortina w/ the racelada stuff, i mean "just use the cortina upright with the raceleda calipers, discs, alloy hubs"...again, IF the capri/cortina stuff will work-with/hook-up-to our wishbones.

[Guest ScotMac]

Also, i assume that racelada is not the only source for this stuff???

[Guest salty_monk]

Rather than negatively questioning the premise (which *IS* *VALID*), does anyone have a positive response to whether the hubs and brakes can be swapped for a nice capri (or cortina) upright and brake assembly like the one i listed in the initial post.

 

Hey... play nicely! Remember on here you're asking for help from a bunch of people who aren't paid to tell you anything...

 

Also do NOT use capitals like that (used for demo purposes only), it seems to be a common American failing forum / email failing & is very condescending.... :angry:

 

 

P.s. 17 stone is 238 lbs... if you're 476 lbs you won't ever fit in a lightweight!