Big Differance between PE and RM forks?

[chamber66]

Forks from either side of 1980. Is there a big differance between the 38mm forks on the PE or the RM?

[knudsen]

It depends what displacement bike we're talkin' about. 79/80 RM250/400 are not the same as 81. Those are long travel for the time. I think about a foot. What differences are you asking about?

[chamber66]

Spring rates, offset  and length etc looking for some beefier forks for my RM370

Edited October 4, 2014 by chamber66

[SMarquez]

I think you are stuck keeping it period correct, especially if you are racing ahrma with it. 79 were longer which would upset your frame geometry unless you went with a 79 arm and shocks. To get the most of your 77 suspension, Race Tech's fork emulators work amazingly well. Your back end will really suck unless you upgrade too. This is the most expensive part of vintage bikes.

[knudsen]

I have the 79/80 RM250/400 front end on my SP. It made a huge difference in handling stability. IIRC the SP forks were 35mm, so you may have a little less to gain in that regard if yours are 36mm as I believe. They are taller than the SP forks, much longer travel, and as SM indicates, it choppered it a bit. I expected that and plan to raise the tail. What I didn't expect was for me to do most of the work for the rear end, and then let it sit for two years! I used an 82 SP drum brake and it's a hell of a lot better than the 85 SP disk brake. Axle offset should be insignificant, all involved are leading axle design. Yoke offset I can get you a rough measure as well as static length, probably tomorrow. Extended length I can get for you next time i work on it. Collapsed length I can't measure until I work on them, probably have to be after Oct. Under the gun at work, and not getting any time off! Springs are very soft, feel softer than the SP springs, lots of dive, but square bumps feel like I have rocks for springs. The shortcomings of damper rods. I have race tech emulators ready to go in as soon as I can get a few days off. You should get some too if you replace the forks, at the same time. Rocky Mountain has them for the RM forks, they have a "S" in the part number which worried me, but a call confirmed that while it indicates street, it's the exact same part and includes the same springs. They puled up the BOM. A lot cheaper from Rocky Mountain and free ship too.I'm keeping the stock springs until I try the emulators, but my goal is not the best off-road performance. I have degenerative disk disease and hope to get more mileage out of my neck and back. Race tech doesn't even list the spring strength, just says "too soft" and has springs ready to sell you. I retained the stock RM steering stem and had to do a little machining. It was 1/8" too long, so I made a simple spacer. RM had all balls and the SP was balls on top, tapered roller on the bottom. SP stem was welded in and I had to grind away a lot to get it out, and I put as much pressure on the RM stem as I was willing to do and it didn't budge, so I did the spacer. Not enough meat on the SP tripples to bore to 38mm and be safe. I went with a new taper roller on the bottom and loose balls on top. It's a $20 trailer bearing I got one delivered for under that price, boxed as Timkens, stamped as made in Japan and same brand as OEM, half the price and no two week delay. I also made a tapered sleeve to press onto the RM stem to essentially raise the area where the bearing sits about 1/4", made a plastic lower grease seal, made some plastic press in spacers so I could add grease zerks and not fill the whole head with grease. All worked wonderfully, just took weeks instead of the days I had planned LOL. Yours is more likely to be bolt on.  Looks like you have two stems available on  the 370, but I don't know what year. Look up your year and do a where used on the part numbers:

 

http://www.suzukipartshouse.com/oemparts/a/suz/50d3917bf8700229982f2d44/front-fork

 

Copy and paste your part no. in here http://www.suzukipartshouse.com/oemparts/c/suzuki_motorcycle/parts click search, then click where used. That will tell you more than any other source as to what will just bolt on.

Edited October 5, 2014 by knudsen

[chamber66]

Thanks for those replies. I am pretty much finished the bike now. and rear is sorted. Over here in the U.K the parts you can use for class elegibility is different to AHRMA. I have a new set of Ohlins piggyback on the rear, so thought I would beef up the front as well. Over here there seem to bbe a lot more 38mm PE forks available, hence the question on length and dampening compared to RM38mm forks

 

And no that tailpipe isn't staying like that

 

 

 

 

 

Edited October 5, 2014 by chamber66

[knudsen]

I was unable to find any information to help me with the swap. Well, I could tell by the allballs conversion charts if the stem was the same diameter. So I just bid at the end of auction when I saw a set that looked rebuildable and not yet bid on. I know parts over there are about double, but if you look for crappy photos and descriptions and dirty parts, then question the seller to make sure he's just too busy to sell in a well presented auction (vs. Butt stupid), you can find a deal well under the going rate. Worst case, clean up and resell. I got the front end, 1999 rear shock with rebound/comp clickers and 2000 swingarm on three auctions for under $100.

That or stalk a PE owner until he gives up the measurements. Check the Pure Enduro page I linked on recent PE threads. Might be some answers there.

I would plan on springs and cartridge emulators if you are racing. Nice looking bike!

[Piney Woods]

I was unable to find any information to help me with the swap. Well, I could tell by the allballs conversion charts if the stem was the same diameter. So I just bid at the end of auction when I saw a set that looked rebuildable and not yet bid on. I know parts over there are about double, but if you look for crappy photos and descriptions and dirty parts, then question the seller to make sure he's just too busy to sell in a well presented auction (vs. Butt stupid), you can find a deal well under the going rate. Worst case, clean up and resell. I got the front end, 1999 rear shock with rebound/comp clickers and 2000 swingarm on three auctions for under $100.

That or stalk a PE owner until he gives up the measurements. Check the Pure Enduro page I linked on recent PE threads. Might be some answers there.

I would plan on springs and cartridge emulators if you are racing. Nice looking bike!

Smart boy. ?