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Discussion in 'Roadster' started by wiztecy, Jan 16, 2015.
The fronts and rears are different sizes. He didn’t put the rears in the front, did he?
Which pads provide the same performance as the Carbotech 1521's - the GS-1 or the R6?
He looked at the boxes and chose one, so I presume he knew which one to look for. I sort of assumed they wouldn't fit right if they were swapped. I'm taking the car back tomorrow morning for a re-coat of the brake quiet stuff, and will ask him to check.
Thinking about the braking performance, I understand that there are improvements that can be made in the strength of the grab. But, with the custom rotors and the GS-1 pads, shouldn't I be able to lock up the wheels with a really firm push on the pedal and the car in Neutral (so no regen)? I am assuming that TC is disabled in neutral, right? During the 60-20 bedding stops, there was no indication of the car wanting to skid, and I was pressing the pedal with a lot of force (nearly standing on it).
I believe the GS-1s are the same as the Carbotech 1521's. That's what I have (the GS-1). Earlier in this thread there was a note that the 1521's were the right ones for normal street use (vs track), so I went back and double-checked, but of course I can't find the reference now.
Greg, I also felt there was not much improvement in braking initially, even after I did a pretty serious bed-in (11 times going 60 to 10). However, after getting some miles on the pads and rotors the braking performance in hard stops is now noticeably better.
Thanks, good to hear. Even now they're at least as good as the originals (except for the noise and clattering), so I haven't gone backwards. Will be driving down the hill on Thursday, and it's supposed to be raining, so will get to check out that angle soon too.
Hello all. GLoc RS-1 pads are the same compound as the 1521. They both take a bedding process, brake pads actually are designed to create friction on a this layer of pad material to work as designed, that is why there is a bedding process. The coefficient of friction of pad material and the iron treatment is lower than the pad material to pad material so folks have found these work better as the bed in.
Another point we have not covered is the importance of cleaning the rotors before installation. All high end rotors are shipped with a protective film on the iron that must be removed, old fashioned soap and hot water with a scrubby sponge is the best way to remove this film. It is possible to use brake cleaner to get this off, but not without scrubbing. The best indicator is that water ‘wets out’ rather than beading up on the surface. If the rotors are not this clean, it will greatly increase the length of time it takes to bed the pad material. If you are struggling with bedding, you can try cleaning the surface of the rotors with a clean scotch bite pad, both faces, and try bedding procedures again. After cleaning the surface of the rotor should no longer look shiny.
The rear rotors will not clear the caliper on the front. We labeled the rotors for location on this batch, marked on the back side, since we had some confusion with a few DIY guys on the last batch.
Thanks for clarifying.
Just to confirm, the mechanic did wash and forced-air dry the rotors before installing them, but I didn't see how he did the washing. Unlikely he scrubbed them with anything abrasive, but after the bedding-in, I think all that surface stuff is gone.
I'll be taking the car in this morning for a re-do of the brake quiet goop. I presume he should remove the old first, before re-application.
Were there any tricks in terms of the front springs? I seem to recall a post earlier that there was some sort of positioning trick to help remove the clicks.
Update.. looks like the clicking sound wasn't from the goo not working, but rather from the pads moving up and down, hitting the caliper case. He's adjusting the spring a bit, and will hold the pads to the top when reassembling things. (This was only a problem on the front right.). Fingers crossed...
I think this was a contributing factor for the delayed improvement on my car. After the installer took the car for its initial bed-in runs there was a definite smell and light smoke coming from the brakes. I suspect that was the protective film burning.
Perhaps a bit better, but still have clacking noise from front right on medium-hard braking. The mechanic is pretty much out of ideas. He confirmed that the pads are firmly positioned at the top, against the caliper housing (perhaps they shouldn't be??). Spring is very strong. Goo was working properly (had to pry the pads off).
The only other thing he can think of is that there might be something odd with the rotor itself, but we ran out of time today to tinker with it (he had other cars to get to). Since this isn't safety related, we agreed to bring the car back early next week for another try, perhaps taking the left front wheel off to compare positions.
Any ideas on what we might have missed? The left front and both rears seem fine.
Thanks Dave, I'm running Carbotech AX (I think - the Autocross pads). I've done some track days and autocross with the car but mostly use it for driving mountain roads in my daily commute. I don't have a problem with fade, it's the initial bite and overall deceleration that's weak (very weak compared to my Lotus Elise - series 1 with unassisted master cylinder - or my wife's Boxster S). When a deer jumps into the road I need to be able to stop. I tend to brake hard every now and again on clear straight roads to make sure the pads are clear of dust etc. I don't have a problem with tire traction, since I'm running sticky wide tires I don't trigger ABS at all.
I would swap out both front and rear calipers to keep it balanced. I also wonder if there might be an issue with low master cylinder pressure that could also be part of the problem?
I found some advice on a lotus forum to use 3M 468MP tape to bond the pads to the caliper. It seems to have eliminated rattles for me.
For what it's worth, the backing plates on what I presume are the car's original pads appear to have been glued on by a manual process, judging by the glue pattern. Especially evident for the front pads, on the right. Picture is of the back of the pad, with the plate removed and flipped over above (so the visible surfaces were mated before being forcibly separated by my mechanic).
If the Brake Quiet goop is working, bonding the pad to the caliper, the tape wouldn't offer anything in addition, would it? The mechanic was thinking that the brake pad was moving back and forth in the same plane as the wheel rotation, and striking the caliper housing when doing so. There isn't anything on the ends of the pads to cushion that.
Having written that, how is that motion taking place? I.e., if the pad is glued to the piston, how is it moving within the caliper housing such that it would strike one end of it? I'm getting more and more confused...
I'll pass on the reference to the tape. Thanks!
If the pad is not tight against the top of the caliper housing then when it brushes against the rotor it will get knocked against the top of the caliper. There was a post by Wiztecy a while ago explaining how a lot of lotus drivers were re-bending the spring that holds the calipers such that the pads would always be at the top which reduced rattling. He cautioned to limit the amount of braking you do in reverse which would loosen the spring again. I haven't tried this because generous amounts of orange goo have prevented rattles for me. I always let it set up for an hour before installing the pads.
Yeah, that's essentially what we tried today. The pad appears to be snug against the top, but it didn't work. I don't know how long he let the goo dry, but it wasn't nearly an hour. Was that the problem?
What I don't get is how lots of goo on the back side will eliminate the pad from hitting the top.
Looking on the Lotus sites, I see that some put rubber pads along that top area to cushion the impact, but it seems like I'm heading dangerously close to recommending he use chewing gum.
For pad installation I put Brake Quiet on the back of the pads like Henry suggests, let it set up for an hour or so. When I load the pads in the calipers I have the calipers off, slide the pads into place and then put the caliper on the car. If I just slide the pads into the front calipers the Brake Quiet gets squeegeed off the back and there is not enough left to hold the pad.
So, one last (?) question: Once the goo dries, and you gently slide the pads back into the caliper housing, being careful to not scrape off the dried goo on the edge of the piston, is there any sort of first thing you need to do before driving off?
What I'm thinking of is to press hard on the brakes before moving the car, so to set the piston into the dried goo before things have a chance to shift. Is that a good idea, or am I making things up based on an incomplete understanding on how things work?
Also, grazing the Lotus forums, some put a rubber padding between the pad and the top of the caliper housing. Presuming that's not needed here, and probably not a good idea to have on one side of the car and not the other.
The car goes back to the shop on Wednesday morning (day after tomorrow). Fingers crossed.