Breaking in Spec Clutch

[brusk]

Anybody tried this process? Sounds like it would be an easier way to breaking in that trying to baby the car for 500+ miles. This is a different platform but I've never heard of a Spec 3+ being compared to OEM for engagement smoothness on any car. Mine is definitely grabby, not as bad as the first 100 miles but still grabbier than I would have liked.

From allfordmustangs forum

I recently read a great article/interview in one of the British hard core race magazines with a tech guy from AP Racing (they make brakes and clutches for some serious race car stuff) where they talked about break in on clutches and how important it is. The AP guy was saying that a 500hp clutch not broken in correctly will get snatchy and could loose as much as 125hp in holding ability. But on the flip side if broken in just right that 500hp rating will go up over 600hp and it will drive very close to stock. I took what I learned from the article and what I have learned from bedding in HUNDREDS of sets of brake pads (very similar to clutches) and came up with a clutch break in procedure and tried it out on my new clutch this past spring. It worked great! My last clutch, the same kind I just put in was horrible compared to the new one. My last clutch went in the car and then straight on the dyno. I’ve bedded in a few like outlined below now and have given the bedding instructions to a few other people. So far it has worked great every time. I thought I would pass it on.

Before you install the clutch scuff the pressure plate and flywheel with ScotchBrite and brakekleen for a fresh surface. This is to remove any clutch material from the previous disc if used and any chemicals or worse case lubricants, etc if dealing with a new flywheel and/or pressure plate. You don’t need to go crazy, just scuff it up. DON’T USE STEEL WOOL!

The clutch break in is easy, just time consuming. The theory behind it is that you want to transfer some of the clutch discs friction material to the pressure plate and flywheel right away. Doing so will increase the clamping force considerably. What you don’t want to do it transfer the bonding agents (glue) in the clutch disc to the pressure plate and flywheel. That will reduce clamping forces a lot. The bonding agents “leech” out of the clutch disc when they are new and subjected too much heat, too fast. If the bonding agents leech out they will “glaze” the clutch and leave a layer, not always even on the pressure plate and flywheel.

So what you want to do is “bed” the clutch in without introducing much heat very quickly. The best way I have found to do this is to “put, put, put” around the neighborhood. Go one block, stop at a stop sign. Go another block, stop at a stop sign, repeat, repeat, repeat. Pull away from the stop signs like an old lady. Remember the key is very little heat so you don’t want to slip the clutch much and you don’t want to load it once engaged (NO hard acceleration). Its easy to tell when things are bedded with brake pads because you can feel it in the “bite” but no so much with the clutch. But its there. You will feel it start to get more aggressive at some point. That is when you have transferred that friction material. I didn’t count my last time out but it took somewhere between 20-40 stop signs. Once it is bedded in park it until 100% cooled down. The cooling process is part of the process. The bonding agents in the disc go though their last chemical change the first time you get heat in it, and that change is not completed till fully cooled.

Once cooled you are ready for normal use. It still wouldn’t hurt to put 50mi or so on the clutch driving “normal” (I.E., slow and boring) though. So if have the time/patience it sure wouldn’t hurt.

I’ve used the above method on a Spec Stage III+, which are known to be snatchy and without a lot of feel and it behaves just like a stock clutch aside from the pedal taking more effort. I can pull away from a stop without even touching the gas the engagement is so smooth. There was no way that was going to happen with the previous clutch (a Spec Stage III+) that was not bedded in properly.

Hope this helps.

[ajm8127]

First of all, clutches are rated in torque, not horsepower. They couple the twisting force (torque) of the crankshaft to the transmission. The speed of rotation (power is torque times speed times a scale factor - 1/5252) is not important as long as it is keep under the maximum allowable limit. The feeling of the pedal has a lot to do with the fact that you have to overcome the spring pressure of the pressure plate to disengage the clutch. You can gain a mechanical advantage with leverage, but you do so at the sacrifice of distance. Your slave cylinder is only going to have so much stroke, so at some point a pressure plate with more clamping force is going to cause the pedal to become stiffer.

I definitely agree with having the proper surface roughness on your flywheel. The roughness is actually needed to ensure the clutch disc conforms to the face of the flywheel. Also the flywheel should be free from any material left by the previous clutch. Most of the time you get the flywheel resurfaced to ensure the surface roughness is correct, remove contaminants, and to ensure the flywheel is nearly perfectly flat. Just like when you change brake pads but keep the same rotors. The rotors should always be resurfaced.

The procedure above specifically says "pull away like an old lady" and "no hard acceleration" which is basically the same things as driving it carefully for the first 500 miles. That said, driving through a neighborhood with lots of stop signs might be a good way to break in your clutch in a controlled manor. You might not be able to control how fast you have to merge onto a highway.

I think some people just have a problem babying the car they just put a clutch like the Spec Stage 3+ in because it is likely a very power car.

In the end I would follow the break in procedure the manufacturer recommends for warranty purposes. If you want to initially do some easy stop and go in a neighborhood, that's fine, but observe the manufacturer's recommend break in interval as well.

[bobS]

I was told by the shop that installed mine, when i had my 335, that it has to be 500 miles of stop and go, not literally 500 miles. So i drove my car for 800 before even getting on it in a aggressive matter just to be safe. It does get better overtime but with a performance clutch, it just won't feel as OEM as the original. I don't understand why some people say its just like OEM because it isn't. I had a spec stg 3+ with smfw. There are pluses and minuses to a performance clutch, its the reality when your car makes double the intended factory hp/tq. I would just follow spec's recommendations..

[ajm8127]

I was told by the shop that installed mine, when i had my 335, that it has to be 500 miles of stop and go, not literally 500 miles.

Good point. 500 miles of high way driving is much different for a clutch than 500 miles of urban or sub-urban driving.

[rudypoochris]

I do about 250 miles or till it feels about right, then I slowly get more aggressive. When it starts getting a little choppy in first gear, I launch it in second to wipe that away and it gets smooth again. That's just what I do, can't guarantee its the best method.

[JoshBoody]

You can break in a clutch fairly quickly... had my spec broken in around 100mi, but gave it another 100mi before multi-gear pulls. OEM clutch was like 50mi. Hard to describe how as its more feel. First part slow, then normal driving with bunch of gear changes... then I start gradually increasing torque but in quick burst and lifting if there's any hint of slip (it will slip a little in the beginning).

[brusk]

I was told by the shop that installed mine, when i had my 335, that it has to be 500 miles of stop and go, not literally 500 miles. So i drove my car for 800 before even getting on it in a aggressive matter just to be safe. It does get better overtime but with a performance clutch, it just won't feel as OEM as the original. I don't understand why some people say its just like OEM because it isn't. I had a spec stg 3+ with smfw. There are pluses and minuses to a performance clutch, its the reality when your car makes double the intended factory hp/tq. I would just follow spec's recommendations..

I understand the driving easy for 500 miles will give you a clutch that will handle the power without slipping I'm more curious if you follow the other procedure could you actually get a clutch that isn't grippy/grabby on engagement. Pedal pressure will of course relate to pressure plate being used that's not a big deal but having a clutch that actually did slip smoothly like an OEM and handle the power would be really nice.

[dzenno@PTF]

Basically, lots of downshifting to transfer material from the disk to the flywheel properly without putting heat into it. 500 miles of driving is recommended but you could probably do it in half of that if all the driving is in the city with lots of stop/go. Either way, I will always bed in my clutch for 500 miles. No shortcuts

[cwarren]

Basically, lots of downshifting to transfer material from the disk to the flywheel properly without putting heat into it. 500 miles of driving is recommended but you could probably do it in half of that if all the driving is in the city with lots of stop/go. Either way, I will always bed in my clutch for 500 miles. No shortcuts

+1 lots and lots of down shifting makes a big difference how it breaks in I'm at 400 miles right now and dying to get on it but have managed to baby it .

[brusk]

Basically, lots of downshifting to transfer material from the disk to the flywheel properly without putting heat into it. 500 miles of driving is recommended but you could probably do it in half of that if all the driving is in the city with lots of stop/go. Either way, I will always bed in my clutch for 500 miles. No shortcuts

I'm not sure if city driving is the best after doing it for the last 300-400 miles. I feel that there's no many short starts where the clutch doesn't even get all the way out. Like when your at a stop sign and have 8 people in front of you, I can tell the difference by the time I get to the light the the clutch seems alot rougher from heating up. Next clutch I'll probably try this method just to see if it makes a difference or maybe somebody else will try it before starting the 500 mile break in. Like I said it's not bad I can live with it but if there's even a possibility of being OEM smooth I think it's worth a shot.

[hokejka]

sorry to revive old thread but are you guys downshifting with rev matching or letting rpm idle and then dragging it out slowly every time

[shushikiary]

I did pretty much exactly what they described here on my SPEC stage 3+ and it worked great. The engagement point a fair amount within the first 40 stop and goes I did, it was very worth it. Then I babied it for 2000 miles (mostly highway) as I am rarely in stop and go traffic. It works great, the thing is a beast, and raising the idle to 920 RPM completely removed all chatter.