Brake Bias for solo. - LotusTalk - The Lotus Cars Community
 
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post #1 of 11 (permalink) Old 09-09-2013, 07:22 AM Thread Starter
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Brake Bias for solo.

Hey -

I have a 2005 Elise that I solo race and don't like the brake bias. I'm sure I'm not alone in this and wonder what others have done to improve the hard/short braking inherent in solo?

dave
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post #2 of 11 (permalink) Old 09-09-2013, 12:31 PM
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Brake Bias

What your referring to as bias may be what others have referred to as Ice Mode, and there is a thread on that subject. Either way there's not much you can do and remain in a SCCA, SS Stock/Street Class, except make sure that your brakes are properly bleed, and all lines and component's are in excellent working condition. If your not concerned about rules then I've seen a proportion valve on Elise Parts that can be installed.

A couple of things that you can do to remain in stock condition is to use different pad (same manufacture) compounds applicable to what you plan to do with the car on the front and rear and of course adjustable shocks can help immensely with weight transfer.

I know these two changes helped the feel and performance of my car.
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post #3 of 11 (permalink) Old 09-09-2013, 04:25 PM
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Yup...experiment with different pads front and rear. Personally, i think the bias is fine. I just need to chuck the crappy Hawk HPS's. i think the stock Lotus pads are much better.

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Originally Posted by Chuck View Post
What your referring to as bias may be what others have referred to as Ice Mode, and there is a thread on that subject. Either way there's not much you can do and remain in a SCCA, SS Stock/Street Class, except make sure that your brakes are properly bleed, and all lines and component's are in excellent working condition. If your not concerned about rules then I've seen a proportion valve on Elise Parts that can be installed.

A couple of things that you can do to remain in stock condition is to use different pad (same manufacture) compounds applicable to what you plan to do with the car on the front and rear and of course adjustable shocks can help immensely with weight transfer.

I know these two changes helped the feel and performance of my car.
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post #4 of 11 (permalink) Old 09-09-2013, 04:42 PM Thread Starter
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Thanks so much for the reply.

I'm running in XP due to some other mods so most anything goes and I don't need to worry about stock class stuff.

I have adjustable shocks and have them set so they do help. I also have mismatched pads with sticky pads in the rear and less so in the front and it helps too but it's still not what it should be. If I ease onto the brakes to encourage weight shift things are better but that is just burning time in solo and would love to be able to get more out of the rear brakes and make the thing drop anchor a bit better.

I was under the impression that one could not use a prop valve along with ABS. The Elise parts site say 'will fit all Elise' but I'd like to know more about the prop valve and ABS. I've written him and asked and also asked the folks that make the part that Elise parts sells.



I have a few paths in mind and don't know what would be best -

* disconnect ABS and install a prop valve on the front circuit and dial it back as needed until I get a mix of front and rear lock up. Then if the valve will work with ABS reconnect it and be happy.

* disconnect ABS and install the Sector 111 bracket in the rear so that I can run a front caliper in the rear. Then install a prop valve in the rear circuit and dial back the now too powerful rears until I get proper balance and then reconnect the ABS if appropriate.

* rip out the entire booster/master cylinder set up and put in a dual circuit set up with a balance bar and call it a day - this option is pie in the sky and I really don't want to go down that road unless I really have to.


Does that make sense to anyone other than me?

Thanks again,

dave
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post #5 of 11 (permalink) Old 09-09-2013, 04:44 PM Thread Starter
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Quote:
Originally Posted by Washburn View Post
Yup...experiment with different pads front and rear. Personally, i think the bias is fine. I just need to chuck the crappy Hawk HPS's. i think the stock Lotus pads are much better.
Interesting - do you race solo? If so do you get the ice mode/abs thing going on under super hard braking?

Thanks,

dave
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post #6 of 11 (permalink) Old 09-09-2013, 05:43 PM
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re: Solo and ABS and Proportioning devices & valves....

I used to Solo I a long time ago.... Here is what I did. It was not a Lotus, but I did get it to be the fastest ASP car in the region without cheating.

1. I assume you have good tires, pads, fluid and disks. It is all a matter of personal preference. I like Castrol SRF, Performance friction (actually offeres specific compounds for front and rear brakes) and two-pice disks or reasonable quality and construction i.e. Brembo.

2. The combo master has a proportioning valve built in. So putting in another valve would be a very poor idea. The proportioning mechanism in the master can be removed. The master will continue to work with equal pressure to back and front. You need to find someone that knows how to do that.

3. Now you can install a prop valve. I think, if you install it out of reach of driver, it is legal. You can practice and pre-set it, anyway. AP unit on EliseParts is precious . Tilton and Wilwood make similar parts. Check out Jegs for about $80.

4. Evans sells a brake dealy valve that you can plumb into the rear brake circuit. It is worth about 1/2 to 1 sec per lap, because it will allow you to run more rear brake.

5. If you do not like the pedal feel. you maybe able to find a larger combo master cylinder with the same flange as stock and replace the stock one. I used to run a Chevy truck one... It had a larger fluid reservoir which prevented the fluid from splashing around too much, as well.

6. You should leave ABS in until you start feeling that you are faster then ABS in detecting impending brake lock-up. You will know when that happens.

7. With larger brakes, delay valves, etc. the brake balance ands the way the car takes a set into a corner will change. I had to re-adjust tire pressures and alignment and the sway bars....

There is nothing wrong with dual-circuit racing brake system witha balance bar, though.

Anton



Quote:
Originally Posted by Davemk1 View Post
Thanks so much for the reply.

I'm running in XP due to some other mods so most anything goes and I don't need to worry about stock class stuff.

I have adjustable shocks and have them set so they do help. I also have mismatched pads with sticky pads in the rear and less so in the front and it helps too but it's still not what it should be. If I ease onto the brakes to encourage weight shift things are better but that is just burning time in solo and would love to be able to get more out of the rear brakes and make the thing drop anchor a bit better.

I was under the impression that one could not use a prop valve along with ABS. The Elise parts site say 'will fit all Elise' but I'd like to know more about the prop valve and ABS. I've written him and asked and also asked the folks that make the part that Elise parts sells.



I have a few paths in mind and don't know what would be best -

* disconnect ABS and install a prop valve on the front circuit and dial it back as needed until I get a mix of front and rear lock up. Then if the valve will work with ABS reconnect it and be happy.

* disconnect ABS and install the Sector 111 bracket in the rear so that I can run a front caliper in the rear. Then install a prop valve in the rear circuit and dial back the now too powerful rears until I get proper balance and then reconnect the ABS if appropriate.

* rip out the entire booster/master cylinder set up and put in a dual circuit set up with a balance bar and call it a day - this option is pie in the sky and I really don't want to go down that road unless I really have to.


Does that make sense to anyone other than me?

Thanks again,

dave
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post #7 of 11 (permalink) Old 09-09-2013, 06:08 PM Thread Starter
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Quote:
Originally Posted by ageshelin View Post
I used to Solo I a long time ago.... Here is what I did. It was not a Lotus, but I did get it to be the fastest ASP car in the region without cheating.

1. I assume you have good tires, pads, fluid and disks. It is all a matter of personal preference. I like Castrol SRF, Performance friction (actually offeres specific compounds for front and rear brakes) and two-pice disks or reasonable quality and construction i.e. Brembo.

2. The combo master has a proportioning valve built in. So putting in another valve would be a very poor idea. The proportioning mechanism in the master can be removed. The master will continue to work with equal pressure to back and front. You need to find someone that knows how to do that.

3. Now you can install a prop valve. I think, if you install it out of reach of driver, it is legal. You can practice and pre-set it, anyway. AP unit on EliseParts is precious . Tilton and Wilwood make similar parts. Check out Jegs for about $80.

4. Evans sells a brake dealy valve that you can plumb into the rear brake circuit. It is worth about 1/2 to 1 sec per lap, because it will allow you to run more rear brake.

5. If you do not like the pedal feel. you maybe able to find a larger combo master cylinder with the same flange as stock and replace the stock one. I used to run a Chevy truck one... It had a larger fluid reservoir which prevented the fluid from splashing around too much, as well.

6. You should leave ABS in until you start feeling that you are faster then ABS in detecting impending brake lock-up. You will know when that happens.

7. With larger brakes, delay valves, etc. the brake balance ands the way the car takes a set into a corner will change. I had to re-adjust tire pressures and alignment and the sway bars....

There is nothing wrong with dual-circuit racing brake system witha balance bar, though.

Anton


Cool - thanks for the comments. I have a few follow ups -

2. Is this always true? I was under the assumption that the bias was set by the relationship between the size of the master cylinder and the slave and by using different sizes front and rear the designer can spec a given bias.

3. I hear you.......that same part can be had stateside for much less.

4. I'd like to know more about this - what is it you are talking about? I don't know who Evans is.

6. I would leave the ABS active if a prop valve would play nice with it........but this is what I'm unsure of.

7. I hear you - I expect i will need to tweak set up if I can improve braking.



Thanks - I look forward to your reply.


dave
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post #8 of 11 (permalink) Old 09-09-2013, 07:05 PM
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re: Brake bias

2. Is almost always true. The production brake systems with combo master cylinder have proportioning valve built into them. The older ones had external fixed valves. A proportioning valve is necessary because:

a. Just the difference in front/rear brake set-up is not sufficient for fine tuning of the brake set-up (for the OEM).

b. Combo master has a common cylinder bore with 2 pistons. Hence, the '2' master cylinders are the same size, whatever that size maybe. A mechanism that connects the 2 pistons which allows them to move at a different rate creates the proportioning to happen. It is cheaper to make (for the OEM) as all built into 1 component instead of an external valve.

4. The delay valve used to be made by Stewart Components. They had a patent for it in the '90's. I think, I saw some still being made by others. I guess it is less popular, now... I am showing my age.

6. ABS works fine with a prop valve. Remember, you have M/C->Prop Valve->ABS module->rear caliper. Hence, ABS does not 'see' the prop valve. It will continue working as it did (it just senses the difference in slip rates i.e. wheel rotation and release and re-applies brake pressure with internal pump. therefore, it is also self adjusting for different pad compounds front-to-rear. The problem that happens when you start going fast and threshold and trail-brake is that stock ABS will start thinking that you have locked up or about to lock-up. While you, the driver, is just in pending lock-up mode, right on the edge of traction. ABS will then kick in and kick you! And You will want to turn it off for good! I turn off my family car ABS in snow storms, since I feel it interferes with my driving... You will know when you need to turn ABS off...) Hence, my comment about the ultimate utility of a production ABS. I ran a prop valve with ABS for years. No difference during ABS activation.

Quote:
Originally Posted by Davemk1 View Post
Cool - thanks for the comments. I have a few follow ups -

2. Is this always true? I was under the assumption that the bias was set by the relationship between the size of the master cylinder and the slave and by using different sizes front and rear the designer can spec a given bias.

3. I hear you.......that same part can be had stateside for much less.

4. I'd like to know more about this - what is it you are talking about? I don't know who Evans is.

6. I would leave the ABS active if a prop valve would play nice with it........but this is what I'm unsure of.

7. I hear you - I expect i will need to tweak set up if I can improve braking.



Thanks - I look forward to your reply.


dave
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post #9 of 11 (permalink) Old 09-10-2013, 09:42 AM
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Quote:
Originally Posted by Davemk1 View Post
If I ease onto the brakes to encourage weight shift things are better but that is just burning time in solo and would love to be able to get more out of the rear brakes and make the thing drop anchor a bit better.
Yeah, I just got back from Nationals, where I finished 3rd in RTR. I'm sorry, I don't have to time to read everything right now, but wanted to comment on this....

This is not true. The reason I can be effective with a stock setup is exactly this reason....easing onto the brakes, and not slamming them. This does not "burn time". You can induce ice mode or ABS by abruptly slamming the brakes, just like you can prematurely shock a tire off it's contact patch be abruptly turning the steering wheel. Breaking earlier and gentler, and setting up for the corner exit is key....you will get the most out of any brake setup by easing onto the pedal.
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post #10 of 11 (permalink) Old 09-10-2013, 01:10 PM Thread Starter
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Originally Posted by Washburn View Post
Yeah, I just got back from Nationals, where I finished 3rd in RTR. I'm sorry, I don't have to time to read everything right now, but wanted to comment on this....

This is not true. The reason I can be effective with a stock setup is exactly this reason....easing onto the brakes, and not slamming them. This does not "burn time". You can induce ice mode or ABS by abruptly slamming the brakes, just like you can prematurely shock a tire off it's contact patch be abruptly turning the steering wheel. Breaking earlier and gentler, and setting up for the corner exit is key....you will get the most out of any brake setup by easing onto the pedal.
I can't argue with your logic and yet it still feels inefficient to me..........if feels like it could be better and that is what I'm striving for. I can and do brake earlier and more gently and the car responds to this and I get my best times this way but any way you cut it I'm driving around the problem.

I've been racing solo for 12 years and have 4 state titles to my name (2 in the Elise in SSP and XP and two in a Birkin S3 in DM) and when I compare the braking in the Elise on slicks to the Birkin on slicks there is no comparison - not even close. With the Birkin it was possible to adjust the bias with a bias balance bar and when set up properly it would allow VERY late braking into the corner with all 4 wheels at the edge of adhesion. The Elise is just not that way and while the issue can be driven around I am trying to figure out how to get rid of the issue. I feel that if the issue is eliminated it would allow deeper braking and faster times.

I know other people with Elise's have complained about the braking and its bias and I just wanted to see how folks addressed it.

Has anyone addressed bias successfully?.......or tried stuff that didn't work?

Dave
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post #11 of 11 (permalink) Old 09-30-2013, 07:09 AM
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In my search to abate the ice-mode issue I tried installing Hawk HP+ pads. They have a really strong initial bite. This didn't change anything at all. This weekend, I put the stock pads on the front and left the HP+'s in the rear. Unfortunately, I also dropped spring rates by a lot and took a bunch of damping out of the shock to match. This clouded the data a bit but I can say that the car brakes MUCH better now and I didn't experience a single ice-mode event.

pretty cool
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