56 replies to this topic

[rik]

rear calipers are heavy as fcuk, front calipers are as light as sh*t

[chris]

Ok, thanks for link, I will try to do this modification in the next futur and I will give you accurate weight of each type of rear caliper ... But, I am doubtful regarding 6 kg saved weight ! Will see !

[Mr_M]

ok the rear of the car is squirming, that shows that the rear is light. Don't forget there is a pic on here somewhere of a vx with just the fronts touching the ground under heavy braking

How about going for a thorney wing to add some downforce to the rear. That should stop it squirming?

Alternatively carry something heavy like a couple of paving slabs in the boot. That should also aid in the downforce.

I'll get my coat...

Must admit I was thinking along the same line as fluffy (although I hadn't made the leap to the paving slabs yet - inspired suggestion ) - maybe the answer is in aerodynamics rather than brake balance?

iirc we are saddled with aerodynamic lift on the back of the car? Surely a wing or decent rear diffuser would help to settle the back end a bit - especially into higher speed corners? Just a hunch from me, but I suspect that kg's and kg's of downforce isn't really required - just something to try and negate the lift? (which is why I'm personally looking to try a diffuser to address exactly the same issue)

[Stu-7]

ok the rear of the car is squirming, that shows that the rear is light. Don't forget there is a pic on here somewhere of a vx with just the fronts touching the ground under heavy braking
How about going for a thorney wing to add some downforce to the rear. That should stop it squirming?
Alternatively carry something heavy like a couple of paving slabs in the boot. That should also aid in the downforce. I'll get my coat...

Must admit I was thinking along the same line as fluffy (although I hadn't made the leap to the paving slabs yet - inspired suggestion ) - maybe the answer is in aerodynamics rather than brake balance?

iirc we are saddled with aerodynamic lift on the back of the car? Surely a wing or decent rear diffuser would help to settle the back end a bit - especially into higher speed corners? Just a hunch from me, but I suspect that kg's and kg's of downforce isn't really required - just something to try and negate the lift? (which is why I'm personally looking to try a diffuser to address exactly the same issue)

Yes, indeed we are affected by lift at the rear. I presume most people know why this is?
(the upswept rear clam does a great job of sweeping up the low pressure air from under the car and channeling it upwards, creating turbulence and lift at the rear – I think TMS quote about 30KG's of lift?) My understanding is that this will affect the car in high speed corners where a confidence dab, or a lift is required on turn-in. It will affect it much less under heavy braking, simply as speed is retarded much faster ergo> the lift is dramatically reduced as speeds drop.
However at faster speeds, with 30 KG's of lift acting on the rear, a confidence dab at 120mph or a blunt lift off the throttle, will shift the weight bias to the front of the car. With 30Kgs acting upwards on the rear, this will obviously translate through the drivers seat/steering wheel – I did notice this at fast corners such as Schwedenkreuz at the 'ring, where you approach at over 140mph, over 2 crests, before brushing the brakes and turning, again, over a crested apex. The thing to remember is, that if the car is well balanced ie: on a trailing throttle, the weight balance will be very close to how it is when the car is stationary viz: 420+ KG's will be distributed across the rear wheels. That's a lot. Reducing that by 30KG's really won't change a thing, UNLESS you are brushing the brakes and turning at 120mph+

Anyway. I digress!
The problem I am referring to, which is specifically under braking, the more I think about it will absolutely be corrected by fitting stronger spring rates to my nitrons.
If I think how the car *feels* when this is happening; it's not that it's about to swap ends (as it would feel if rears were locked) it's just that there's <relatively, compared to a road car> so much "dive" that the rear starts to track as badly as the front, almost weaving.
The dive is cause by the springs compressing. Increasing the compression force on the damping will only mitigate this by a small amount; the answer I am sure of it is stiffer spring rates.

Edited by Stu-7, 02 March 2007 - 08:04 PM.

[siztenboots]

the main advantage with them is the 3 kg(!) less unsprung weight per side at the rear...

Could you clarify ?

I can't see, how you can save 3 kg per side, only by replacement of rear calipper, even with ultralight caliper, what is the weight of OEM rear calipper ?

4 kg according to this link
Here

Yep, the Hispec ultralites weigh less than 1KG, ~800gms , so total saving per wheel 3.2KG unsprung mass , best bang for buck I could find.

[chris]

This Hispec ultralite rear brake for VX220, is a chimera, it does not exist yet, and may be shall never exist ! It is announced since one year ... I send several mails and reminder without any reply from Hispec. Moreover, I heard this company seems to have odious reputation. It is a pity, because it was a good idea ...

[meldert]

This Hispec ultralite rear brake for VX220, is a chimera, it does not exist yet, and may be shall never exist !

It is announced since one year ...

I send several mails and reminder without any reply from Hispec.

Moreover, I heard this company seems to have odious reputation.

It is a pity, because it was a good idea ...

There is an alternative though... Eliseparts have the same rear caliper (made by hispec but with specifictions from eliseparts) and last time I asked them they had them in stock. The difference is that they are radially mounted (as our front calipers) but there is an adaptor kit that will fix this. the downside is that this will be a more expensive solution then the hispec ones.

elisparts Lightweight Rear Caliper £350 + VAT

elisparts Radial Caliper Mount Brackets £71.95 + VAT

finally you'll need a different hand brake cable (I guess you would need this one with the hispec calipers too):
elisparts Handbrake Cable (for Lightweight Rear Calipers) £71.95 + VAT

[chris]

I contact them (Elisepart) and I had understood that it necessary to adapt these specific caliper to their specific alu rear hub.

Edited by chris, 13 March 2007 - 04:52 PM.

[Arno]

elisparts Lightweight Rear Caliper £350 + VAT

elisparts Radial Caliper Mount Brackets £71.95 + VAT

finally you'll need a different hand brake cable (I guess you would need this one with the hispec calipers too):
elisparts Handbrake Cable (for Lightweight Rear Calipers) £71.95 + VAT

Unfortunately that does not work.

The adapter braket ONLY fits on the original aluminium rear uprights of the S1 Elise:



It will NOT fit on a steel upright like the later S1's, the S2 Elise and the VX/Speedster. The knuckle mount of the original brake caliper is too close to the edge of the disc to be able to fit a bracket and still get the caliper to sit properly.

For the brake caliper to fit here you also need to fit the rear GT uprights from Eliseparts:



But those are almost 1000 pounds ex VAT a set..

(don't let the studs on the hubs fool you. These are S2 uprights, but with a bearing pack/hub that has been fittted with studs like the S1 instead of bolts like the S2/VX)

So yeah.. it can be done, but it's very expensive..

Bye, Arno.

[meldert]

Arno, you are ofcourse right, I just realised that too and was about to point it out... But there should be a way to fix an adaptor I think. I will have a look at dudes race speedster, he uses the original front calipers (which have similar mounting) at the back on the original uprights with an adaptor and he used to have the original size on the brake discs. There should be a way around it... But since the calipers that eliseparts sell are really made by hispec there must be a way of getting the ones with axial mounting instead... It's a pity that hispec seems to be so hard to contact... Maybe we should talk to B.A.D, he mentioned somewere that they were going to use Hispec calipers on the badster, maybe he has had more luck in his contacts with hispec?

[Arno]

But there should be a way to fix an adaptor I think. I will have a look at dudes race speedster, he uses the original front calipers (which have similar mounting) at the back on the original uprights with an adaptor and he used to have the original size on the brake discs.

Yup.. I haven't looked very deeply into it, but did discuss it with Geary and looked at 'big brake' kits for other cars (eg. from Movit' ) that often use this sort of bracket to convert knuckle to radial mount.

Geary mentioned that if bigger discs were fitted then it should be no problem to make an adapter bracket. On normal size discs it gets quite tight. Bit of an expensive gamble to buy a set to 'see if it can be made to fit' though..

There should be a way around it... But since the calipers that eliseparts sell are really made by hispec there must be a way of getting the ones with axial mounting instead... It's a pity that hispec seems to be so hard to contact... Maybe we should talk to B.A.D, he mentioned somewere that they were going to use Hispec calipers on the badster, maybe he has had more luck in his contacts with hispec?

Yeah.. HiSpec is notorious for having utter lack of customer support and interaction. Perhaps B.A.D. do have some contact inside HiSpec who does respond. They should start (re)selling these.. Seems to be lots of interest

Also interesting is that the german version of HiSpec also sells these rear brakes, but (are you sitting down?) for EUR 1.425,00!!! (and not 155 pounds per caliper like the UK guys..)

http://www.hispec.de/opel.htm

But here the rear ones are also still listed as 'under development'.. Interesting as the last time I asked they said they would be available in September 2006.. So much for that idea..

Bye, Arno.

[Dominique]

Yup.. I haven't looked very deeply into it, but did discuss it with Geary and looked at 'big brake' kits for other cars (eg. from Movit' ) that often use this sort of bracket to convert knuckle to radial mount.

I've tried Mov'it and got a reply that they don't have upgrades for the VX220...
Not an answer I'd like to hear, but at least they respond

Edited by Dominique, 17 March 2007 - 07:17 PM.

[manus]

This Hispec ultralite rear brake for VX220, is a chimera, it does not exist yet, and may be shall never exist !

It is announced since one year ...

I send several mails and reminder without any reply from Hispec.

Moreover, I heard this company seems to have odious reputation.

It is a pity, because it was a good idea ...

Well, I've mounted them today, so I'm sure they do exist
Will do some serious test driving next week Wednesday 19th on the Zandvoort circuit .
Weight of these calipers is 1.2kg, saving 2.5kg per wheel over the original 3.7kg .
Using the ultra light Speedlines with Yokohama 048's and Ohlins 2-way shocks.
Front wheels are equiped with AP big brakes, engine is EVO360 Vmax tuned to 360bhp/500Nm , weight of the car is 875kg approx, so try and beat this car on the circuit (provided I find a better driver than myself)

Attached Files

•  hi_spec_small_1.jpg   73.88KB   2 downloads
•  hi_spec_small_2.jpg   104.21KB   1 downloads
•  hi_spec_small_3.jpg   82.04KB   1 downloads

Edited by manus, 10 September 2007 - 06:53 PM.

[slindborg]

I hope the calipers are reliable for you manus... many of the homebrew hispec calipers are known to stick etc.... so keep a sharp eye out on that.

[Richy]

R1CHY knows better, I am sure, but in the dry under heavy braking the rear brakes of a bike are next to useless as there is no weight at all on the rear tyre.... ON R1CHY's it is probably 30cm in the air!

Sadly im the oppisite, im all back brake [years of motocross drummed it into me] hence why i just had to uprated an already great slipper clutch - i feel more at home entering sideways

Can't you get an adjustable bias box for the VX then? I've had them fitted to nearly every rally car i've owned I'm sure Peter Llyod [race and rally shop ] could source someone to make some up.

In my experience having too much rear pressure will end in a spin, i personally would dream of fitting stronger rear brakes to a track car - rally car yes, coz its all about drifting around those corners, but track car no, it would up set the balance way to much..

Stu, stiffer spring rates are definitely the way to go - and if your damping is adjustable then tweak and play till your happy with the set up.

Edited by R1CHY, 10 September 2007 - 08:05 PM.

[manus]

Had the installation done at my local Opel (=Vauxhall) garage. No problem at all. I have not yet prepared a new handbrake cable (old one does not fit) but when re-using the old one (adjustment parts) and 2 x Corsa-B (Opel part#522615) handbrake cables it should be a piece of cake (I don't use the handbrake ever, but need it when yearly inspection takes place).
The DS2500 pads make too much noise (screaming ) and the pads rattle when driving slowly. I will replace the DS2500 with Pagid RS14 and have ordered a pair of anti-rattle clips. Will solve both inconveniences I'm sure.

So far I'm pleased with the results. Had a 4 hours of fast driving at the Zandvoort circuit last week with lots of fun no problem at all. Will have another go at the Nurnburgring next weekend but I don't expect any problem.

Specs of the car: 360bhp EVO360, Yokohama 048's, Speedline ultralight 16"/17", Ohlins 2-ways, AP big-brake 308mm at the front, big rear wing, front splitter and approx. 875kg.

Attached Files

•  E2E55040676111DC85A1999AD9888FA9.jpg   55.56KB   0 downloads

Edited by manus, 25 September 2007 - 06:25 PM.

[chris]

This Hispec ultralite rear brake for VX220, is a chimera, it does not exist yet, and may be shall never exist !

It is announced since one year ...

I send several mails and reminder without any reply from Hispec.

Moreover, I heard this company seems to have odious reputation.

It is a pity, because it was a good idea ...

Well, I've mounted them today, so I'm sure they do exist
Will do some serious test driving next week Wednesday 19th on the Zandvoort circuit .
Weight of these calipers is 1.2kg, saving 2.5kg per wheel over the original 3.7kg .
Using the ultra light Speedlines with Yokohama 048's and Ohlins 2-way shocks.
Front wheels are equiped with AP big brakes, engine is EVO360 Vmax tuned to 360bhp/500Nm , weight of the car is 875kg approx, so try and beat this car on the circuit (provided I find a better driver than myself)

Where have you bought them and how much ?
(Hispec UK never answer to my mails ...)

For handbrake cable modification, I see one which may be could be suitable for this application on Elisepart website :

http://www.elisepart...products_id=609

Regarding weight of OEM rear caliper, I found only about 3kg !



But 2 x 1,8 kg = 3,6 kg saved, on unsprung weight, it is already a great deal for me !

Edited by chris, 26 September 2007 - 04:22 AM.

[manus]

Where have you bought them and how much ?
(Hispec UK never answer to my mails ...)

For handbrake cable modification, I see one which may be could be suitable for this application on Elisepart website :

Regarding weight of OEM rear caliper, I found only about 3kg !
But 2 x 1,8 kg = 3,6 kg saved, on unsprung weight, it is already a great deal for me !

Chris, the difference in our measurements is with/without pads.
I'm not sure if I've added pads on the new ones in my weight calculation so your 3.6kg is likely to be correct.
You will defenitely FEEL the difference on unsprung weight .

I've bought them at bigbrakes.com, there was not much interest in a group buy, so there was a small penalty on top of the prices quoted on:
http://www.vx220.org...bigbrakes&st=40

Edited by manus, 26 September 2007 - 06:15 AM.

[chris]

Thanks, I will contact them !

[jonasb46]

However at faster speeds, with 30 KG's of lift acting on the rear, a confidence dab at 120mph or a blunt lift off the throttle, will shift the weight bias to the front of the car. With 30Kgs acting upwards on the rear, this will obviously translate through the drivers seat/steering wheel – I did notice this at fast corners such as Schwedenkreuz at the 'ring, where you approach at over 140mph, over 2 crests, before brushing the brakes and turning, again, over a crested apex. The thing to remember is, that if the car is well balanced ie: on a trailing throttle, the weight balance will be very close to how it is when the car is stationary viz: 420+ KG's will be distributed across the rear wheels. That's a lot. Reducing that by 30KG's really won't change a thing, UNLESS you are brushing the brakes and turning at 120mph+ This i think is a very interesting point, if someone finds a setting thats make the Speedster more setteled over Swedenkreutz, and prevents it from going sideways towards the slope after Pflansgarten (not a good place), than a Porsche GT3, i would be very pleased to copy the settings. The German Speedster guys i´ve been talking to says you cant have short track camber and caster, especially on the rearweels, or the car will be unplanted and not for Ring use!! Anyway i think the problem is best solved by not worrying or letting of the gas... A couple of more inches between the wheels (front/rear) should do the difference... /jonas.