radial mount calipers with parking brake - LotusTalk - The Lotus Cars Community
 
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post #1 of 13 (permalink) Old 08-07-2015, 09:51 AM Thread Starter
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radial mount calipers with parking brake

On my autocross car I have the eliseparts 40mm drop uprights front and rear.
The rears support radially mounted calipers only. I assume that is a good part of why most are using the 16mm drop or the sector111 uprights for the rear, because they let you use the stock rear caliper.

This is a problem because the vast majority of radially mounted calipers (especially lightweight ones) do not support a parking / emergency brake. As required by the solo rules you are suppose to have a redundant emergency brake.

So, what I did was source a 4 pot caliper with about the same piston area as the OE caliper from Wilwood that has a modification for the parking brake. This piston has roughly the same clamping force as our stock caliper but weighs several pounds less due to aluminum construction. The OE rear caliper is a heavy POS.

I think it is the same as what flyinmiata uses for their rear calipers on their BBK but I sourced the part from wilwood overseas. This required different rotors as well, as the calipers require narrower rotors. I ended up using rotors intended for a mini cooper that have the 4x100 pattern, after experimenting with 3 other sets of rotors for various 4x100 cars. Mini rotors were very cheap fortunately so that offset some of the cost of this endeavor. Also they weigh considerably less than Lotus rotors as they are not vented and smaller diameter.

This was still not exactly a bolt on deal, there are spacers behind the rotors to get them to line up, some washers to get the caliper to line up right, and then centering ring was fabricated so my hub where the mini rotor sits is mini sized. Different rear brake cables, both the hydralic and the parking brake cable were needed to as the fittings are different than stock.

Unfortunately I didn't keep track of the total weight savings exactly but it is somewhere in the ball park of 5lbs per side of unsprung weight.

If someone else wants to go down this path I could probably put everything together as a kit and save them a lot of R&D and money buying and returning parts.




2005 Lotus Elise turbo k20a2 757whp 536wtq 31psi [email protected]
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2007 Lamborghini Gallardo Spyder
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post #2 of 13 (permalink) Old 08-07-2015, 10:58 AM
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Nice, I did a similar install on my STR S2000. Same caliper, designed my own two-piece rotors, made flange-to-radial mount adapters... ~12 lbs of overall weight savings.

For what it's worth, you could design/make spacers to widen the Wilwood caliper and allow the use of the OE rotor... or whatever rotor you want. This is how Wilwood accommodates different rotor widths with many of their calipers. I contacted Wilwood about this and they said it should work fine, but will void any warranty for the caliper.

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post #3 of 13 (permalink) Old 08-07-2015, 11:34 AM
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Brembo Makes an aluminum hand brake caliper which looks pretty good...

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post #4 of 13 (permalink) Old 08-07-2015, 11:40 AM
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StopTech makes an aluminum one also....

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post #5 of 13 (permalink) Old 08-07-2015, 12:04 PM Thread Starter
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jdawson:
I am pretty sure I could get calipers from wilwood that would allow rotors the width of the stock lotus rotor
I opted not to because mini and miata rotors are much cheaper than lotus rotors, and weigh substantially less to boot

boxershorts:
Correct me if I am wrong but those you show there are not radial mount, therefore don't bolt up to the ep 40mm uprights

For whatever you call that mounting style that the OE upright is, flange?, there is a bigger selection of handbrake appropriate calipers
Another concern is the selection of pads. Some of the handbrake calipers there aren't a lot of choices, and possibly 0 race appropriate compounds available
These wilwood powerlites you can get any porterfield or raybestos compound


2005 Lotus Elise turbo k20a2 757whp 536wtq 31psi [email protected]
2005 Lotus Elise 2zz supercharged 'streetable' race car
2007 Lamborghini Gallardo Spyder
2010 Ford F350
2004 Mazda RX8
2007 Mazda Mazdaspeed 3
2010 Ford Fusion Hybrid
I passed my license test in a 3cyl 70hp Geo Metro
I learned to drive a manual on a Lotus Elise

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post #6 of 13 (permalink) Old 08-07-2015, 12:24 PM
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Quote:
Originally Posted by dallasreed View Post
jdawson:
I am pretty sure I could get calipers from wilwood that would allow rotors the width of the stock lotus rotor
I opted not to because mini and miata rotors are much cheaper than lotus rotors, and weigh substantially less to boot
Ah, gotcha. I misunderstood - thought you went with the solid rotor in order to accommodate the narrow caliper.

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post #7 of 13 (permalink) Old 08-07-2015, 12:47 PM
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this is what run. 4 pounds lighter than stock. aftermarket parking brake
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post #8 of 13 (permalink) Old 08-07-2015, 01:11 PM
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Nice setup, I had not seen the Wilwood with the integral parking function before.

The Brembo parking caliper is super expensive!!! ~$1000 IIRC.

The Stoptech is ~$350 last I looked.

The Wilwood mechanical Spot is $76 and super light.




It basically needs a bracket to mount it to the hub, and a clamp to hold onto the cable and a spring and a bracket to react the cable force.



I had to design my own


I used plastic to mock everything up

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post #9 of 13 (permalink) Old 08-08-2015, 12:51 PM Thread Starter
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Originally Posted by jdawson View Post
Ah, gotcha. I misunderstood - thought you went with the solid rotor in order to accommodate the narrow caliper.
Honestly it was a bit of both. When I got the caliper from wilwood initially and it was too small to fit the OEM rotor I thought it was a problem. I had thought I ordered the correct part that would fit our rotors. I did some looking and realized it was an opportunity to save more weight and switch to cheap rotors. I figured why not use what I already have. The fabrication and such probably ate up a good bit of the cost savings but what the hey.

I can't remember but I am thinking the mini rotors ended up being something like 100 for the pair, quite a bit less than the BOE floating rotors I have in the front. The wilwood calipers weren't the cheapest at a bit over 500 I am thinking then about 100 in other stuff.

Whether or not the car actually substantially benefits from vented floating rotors in the rear I guess I will see, but for autocross I think the lighter weight is more pertinent and this will be the more optimal setup overall as far as where you prioritize the compromises.

2005 Lotus Elise turbo k20a2 757whp 536wtq 31psi [email protected]
2005 Lotus Elise 2zz supercharged 'streetable' race car
2007 Lamborghini Gallardo Spyder
2010 Ford F350
2004 Mazda RX8
2007 Mazda Mazdaspeed 3
2010 Ford Fusion Hybrid
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post #10 of 13 (permalink) Old 08-10-2015, 08:22 AM
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This thread is cool. Dallas, it looks like you're making some neat strides.
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post #11 of 13 (permalink) Old 08-10-2015, 09:36 AM
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Quote:
Originally Posted by dallasreed View Post
jdawson:
I am pretty sure I could get calipers from wilwood that would allow rotors the width of the stock lotus rotor
I opted not to because mini and miata rotors are much cheaper than lotus rotors, and weigh substantially less to boot

boxershorts:
Correct me if I am wrong but those you show there are not radial mount, therefore don't bolt up to the ep 40mm uprights

For whatever you call that mounting style that the OE upright is, flange?, there is a bigger selection of handbrake appropriate calipers
Another concern is the selection of pads. Some of the handbrake calipers there aren't a lot of choices, and possibly 0 race appropriate compounds available
These wilwood powerlites you can get any porterfield or raybestos compound

They are not radially mounted... I think they call them caliper "ears" or ear mounted.

I guess EP was only thinking about racing when they designed those uprights...
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post #12 of 13 (permalink) Old 08-10-2015, 09:58 AM
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Those are called "Lug mount" when they have the mounting bolt holes on a flange at 90 deg. from the rotor direction.

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post #13 of 13 (permalink) Old 08-10-2015, 12:04 PM
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OK... it appears that they call it the same thing on the other side of the Atlantis too... now.
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