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Message started by Dave on 05/22/18 at 05:11:57

Title: Testing Clutch Springs
Post by Dave on 05/22/18 at 05:11:57

Does any of our members have the ability to measure spring pressure?

I installed a set of EBC clutch springs that claim to be 10% stronger than the stock spring set. The EBC springs actually have a slightly smaller wire diameter - but are a bit longer. I don't know if they are stronger once installed, as the force on the clutch lever really doesn't feel any stiffer.

Does someone on this forum have equipment that would allow them to compress the spring to the installed length and measure the force?

Title: Re: Testing Clutch Springs
Post by hotrod on 05/22/18 at 10:38:39

I installed the EBC springs and got clutch slip. Ordered the stock springs, and have no slip. Don't know what rates they were.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 05/22/18 at 13:23:54

Take some measurements and figure out the installed height of the stock spring. It should be the same for the new spring. Place a bathroom scale on the table of your drill press. Place a piece of 1/8 to 1/4" aluminum plate on the scale to distribute the force evenly. Zero out the scale. Use the micro-feed on the drill press to compress each spring (stock & replacement) to the installed height, then take a reading from the scale. Compare the readings.

If you want to get fancy, check each spring at installed height, then compress in small increments (say 1/8" or 1/4"). Take several readings, then plot on a graph. As long as they are not progressively wound springs the spring rate should be linear.

Let us know the results of your test.

Title: Re: Testing Clutch Springs
Post by GT61 TURBO ZX14 on 05/23/18 at 09:23:30

I put some brunette Springs and I believe and there stiffer but my stock ones where shot so it's hard to tell but with the big bore 97mm and cam and shaving 40 out of the jug. And me being 375 if I hit it the clutch did slip a Lil then I took the Rotella oil out and put my motul 7100 in and it hasn't slipped yet I think I am still going to make them stiffer

Title: Re: Testing Clutch Springs
Post by Ruttly on 05/23/18 at 11:55:32

I Always use blonde springs ! ;D ;D ;D

Title: Re: Testing Clutch Springs
Post by justin_o_guy2 on 05/23/18 at 14:28:18

I test them every time I ride.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 05/23/18 at 23:02:24

I had my clutch cover off to revisit the chain tensioner, so I opened up the clutch and checked out the springs. The bike is a 2016 and only has a little over 1100 miles so these springs should be pretty close to new. Here's the data.

Free length: 35mm
O.D.: 20mm
I.D.: 14mm
Wire diameter: 3mm
Installed length: 28mm
Force @ 28mm: 42 lbs +/- 1 lb

Title: Re: Testing Clutch Springs
Post by Dave on 05/24/18 at 02:30:10

Send me your mailing address in a PM....and I will send you a pair of the EBC springs to test!

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 22:56:38

So Dave sent me the springs. He sent 2 stock springs and 2 EBC springs. In the mean time, I ordered a set of EBC springs from Dennis Kirk, so I had lots of springs. Let's get started.

First I did a visual inspection of Dave's stock springs (don't know if they were new or used). My visual criteria for a good spring in this application is it must be perpendicular (i.e. stand up straight) and it must be free from visual defects.

The stock springs looked pretty darned square.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 22:58:33

And the end grinds looked nice. I also didn't see any cause for concern in the windings. The stock springs exhibited typical Japanese quality.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 22:59:58

Then I took a look at his EBC springs. The perpendicularity was a bit off.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 23:00:42

And the end grinds were pretty funky.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 23:02:36

Is this sort of quality control typical of the EBC product??? Let's take a look at the EBC springs I received from Dennis Kirk. Perpendicularity? You be the judge.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 23:03:47

Visual of the end grind. Yuk!

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 23:24:03

Just based on the visuals of the EBC product I doubt I would install them. But lets move on to the actual spring constant tests. Note that the dimensional inspections came out OK. The EBC springs can probably be installed without grinding or filing on anything. So how did the spring force at installed height check out.

I checked the stock springs first. They were 39 lbs @ installed height (28mm), 44 lbs at 27mm, and 48 lbs at 26mm. That works out to a constant of about 4.5 lbs/mm. They were about 2 lbs shy of almost new springs but what the heck, they're used.

Then I checked Dave's EBC springs. They were 39 lbs @ 28mm, 43 lbs @ 27mm, and 48 lbs @ 26mm. Again, a spring constant of about 4.5 lbs/mm. Note that the new EBC springs apply the same pressure at installed height as a used stock spring, and 2 lbs less than a stock new spring.

Then I checked a couple of my brand new, right out of the sac, EBC springs. They dialed in at 24 to 25 lbs at 28mm, and went to coil bind at 40 lbs. I didn't even bother to measure the height. It was such a gross disparity that it didn't deserve any sort of measurement. A picture is worth a thousand words.

Title: Re: Testing Clutch Springs
Post by DragBikeMike on 11/09/18 at 23:31:06

Now that I look at the picture I see that I was generous with coil bind at 40, its actually 38 lbs.

The quality control with this product is woefully inadequate. Perpendicularity is very important. If the ends of the spring are not ground square you will have rubbing and binding. The spring may not apply pressure in a linear fashion. The crude grinding on the ends of the spring create all sorts of stress risers. Some of the springs going into coil bind before you reach installed height force is a recipe for failure.

When I need new clutch springs I will be looking to OEM or a different aftermarket supplier.

Title: Re: Testing Clutch Springs
Post by justin_o_guy2 on 11/10/18 at 01:41:13

As much as I appreciate clamping force, I've seen enough sintered metal throw outs turn into splintered metal in need of throwing out to not want to increase the odds.
IMO, if it's not slipping, it's not something to be doing.
Unless you're gonna whittle out a billet part.
I would totally hang one on the wall if Someone wanted to build a few.
The oem part is designed without using radius stress relief. Just hard corners.

Looks like Armen got a hold of Mike's test block.