Author Topic: Shock length for Carbon (and all?)? (Read 5870 times)

jazclrint · « **on:** April 24, 2005, 06:13:26 pm »

Again,
I am finding these archives not particularly giving of info. Being from the Motorcycle world as well I am very sensitive to shock lenght and ride height. Which I would think is even more important on a Mt bike for clearence reasons. Now, I finally found the stock lenth of the Noleen shocks (8.25"/209mm). I'm looking at some Fox shocks that are 7 7/8"/200mm. I want to replace the front and rear because I love my Girvin froks for their rgidity, and light weight. I have not ridden my 5500 as much as I like, and not really fine tuned the suspenions preload, but I find the turning to be not quite there. It just doesn't quite want to carve the corners as I'd like. But the front end seems quite twitchy. My old 2000 gave the same feeling. If I was on a motorcycle I would increase rear ride height. What do you all think of that issue, and, how much ride height will I loss if I go with 9mm shorter shocks front and back? And, does the Fox's extra 6.4mm of travel help compensate for its 9mm less shock length? And as far as up front I know I am dissagreeing with Andrew, but I believe that ALL the Noleen NR-X shocks were the same lenght, and a shorter shock could cause some weird geometry issues.
Thanks all.

shovelon · « **Reply #1 on:** April 25, 2005, 03:02:53 am »

I found my crosslinks also were a bit twitchy. Especially when braking on turns and switchbacks. I reckoned that the j path on brake dive was shortening my wheel path and I could feel the rear wheel hopping a little. It gave me the feeling that I was about to endo anytime.

So I agree with you somewhat that lowering the bottom bracket via the rear shock could reduce the j-path twitch. Whether it will carve better, that goes against my logic.

Terry

jazclrint · « **Reply #2 on:** April 25, 2005, 10:44:58 am »

I don't beleive its the fork, and I don't ever feel like I'm going to endo. I'm talking more in nice flowing curves, or just cornering at any kind of speed, it just doesn't carve the corner the way I think it should/could.

But I am curious of those who have changed shocks, what lengths they've used.

Simon · « **Reply #3 on:** April 25, 2005, 11:09:31 am »

I've riden an Evo (same geometry as carbon frame) running a 190 i2i sid shock with 80mm travel fox fork,I wouldn't say it improved cornering,being quite tall 6'1" I felt I was sitting in the bike and not on it,also had an issue with the cranks fouling the ground,ProflexGB who's bike it is found it suited him fine,he is shorter than me,I found my 4500 excellent on fast cornering though I have ditched the flexy carbon s/arm in favour of a converted aluminium version,I always found slow cornering a little bit unweildy,though I put this down to me running a very high saddle height,also coming from a MX back ground I would set the rear suspension more compressed on fast corning thus slackening the head angle making the front end less twitchy,IMHO thats where I'd start,but setup is a very personnal thing.
Simon.

Frankd3000 · « **Reply #4 on:** April 25, 2005, 11:52:20 am »

Jaz - my latest P.M. to you will help you to understand a little better.

I agree with Simon, in that set-up is VERY personal. I lived with a Rock Shox Mag21 and Quadras (remember those?) way back when. I didn't like them. My biggest problem was the stiction found in the legs. I could ride and see the legs flexing - not very reassuring, to say the least. This was on a different bike, so it's only so relevant, but I still prefer the advantages of the Noleen over telescopics.

With the Noleen I did find it twitchy, but I like it. There's virtually no flexing of any kind and the endo feeling that many speak of - I don't notice it. At least not as an endo, per say. I always thought the feeling had more to do with the frame/fork geometry and the rake of the fork. JMHO.

As for front shock i2i - disagree as you may, I can prove that it is VERY different from set-up to set-up, and why.....

Ever notice on the CrossLink Install Helper page that there are two ULM's (67 and 80, for reference)? Have a look at pics - there's really three. Carbon forks, from what i've seen, have a shorter one then the 67 mm piece (typcally found on the Way Big bikes). Keep this in mind....

Take a look at the head tube heights out there and you'll find that there is NO specific correlation between head tube height and which ULM is absolutley "the one". K2 lists their "critical "dimension" and even puts in a sublte disclaimer - "You may find headtube measurements that fall out of the specified range and still work". Interesting, huh?

So, what does all this mean? There's no TRUE absolute that says "mine is right and yours is wrong". It's almost bike-specific. Take a look at some of the measurements that have been looked for lately - axle to crown and front shock i2i, mostly. I suspect you'll find there's a range of sizes, even within the same frame type. I've seen of Carbon fork on a frame with an OE ULM and another with one which "supposedly" (mocking myself) should be on a Carbon frame.

Now, keep in mind, this is all coming from what i've seen in pictures, but they DO speak a thousand words. I haven't gone out and measured hundreds of frames/forks to back up what i'm saying, but if you look closely at pics you can see it occurs.

For reference, my combo....

'98 3000, Way Big, ELT with Noleen NR-2 measuring 9.75" i2i (148 mm), using the shorter, 67 mm OEM ULM. It doesn't get any longer than that shock, from what i've seen.

Not arguing, not flaming or ANYTHING of the sort. Call me Mulder, looking for the truth. Don't mean to hijack, Jaz, or offend. This is what i've come to understand and i'm "putting it out here" to compare notes and discuss.

Read my P.M. - DON'T buy anything yet, please. At least let me be the Ginuea Pig (sp?) and see what happens and let it be my time and money spent. If it works out good then let's tackle yours. The front should be done by this weekend and I'll be completely done in mid-May.

BTW - from what i've found, raising the front by 1" reduces headtube angle by about 1 degree, if you don't touch the rear at all. Don't quote that, it's just a quick measurement.

jazclrint · « **Reply #5 on:** April 25, 2005, 01:12:31 pm »

Ok, cool. That's definately enough fo me to think about for a while.

I'm posting just as a refference for other's in the future. First question, when you wrote "9.75" i2i (148 mm)" what was the mm reffering to? Because 9.75=247.65mm. Just so you know my set up, I got my frame with 2 sets of shocks. One set of smarts (NR-5), and one set of NR-2s. All four of them are 8.25". And the guy I bought the frameset from said that all the carbon frames were the same except that they were stretched horizontally. So the swing arm and head angle and fork geometry's should be the same accept for the wheel base. I am also aware of the different link forks. Mine was the newer one that linkage was changed to make the fork travel a little more user freindly. I believe that was changed on all of the '98s, as I had a buddy that had a girvin and confirmed that my '98 2000 had the new travel path/linkage. He also pointed out that my Girvin had a longer head tube than his, as his was built for other bikes to use and not my Proflex. So it makes sence that they would use the same shock and change the geometry around it. But that is obviously not the case. Is any of what I heard about right?

So what are you doing. Making extentions to make the shock lenght right?

Thanks.

jazclrint · « **Reply #6 on:** April 25, 2005, 03:06:19 pm »

Not to piss you off, but it was already kind of too late (for atleast one shock). I got a set of Fox Float RL AVAs on the way for $215 each. They are 7 7/8"/200mm long each. That is 9mm or 3/8 short on each end. I read in the shock fit guide that 10mm doesn't do too much on the rear. And they are brand new so if I don't like the set up I'm know I can recoop my money no problem. Or atleast most of it.

But in your opinion what will the missing 9mm do front and rear I am thinking that if you only get 3" out of 1.75" of shock travel, up front, verses 4.7" out of the same 1.75", the rear will sit lower than the front. And I'll be lower all together, but how much? I asked Fox if there was a way to get an extra 9mm, but I seriously doubt there is. I'm waiting on their reply. I'm going to go measure some fixed points and record them and then I'll be able to compare.
Later,

Frankd3000 · « **Reply #7 on:** April 25, 2005, 03:36:46 pm »

Correct, 9.75" = 248 mm. Simple error on my part, sorry for the confusion. I gotta stop converting to mm, or at least be more carefull. Many apologies.

You're getting the hang of it, as far as some of the variables are concerned. There's some mix-and-match involved between frames and forks. As I said, there's nothing to say which is right or wrong. Sad, but true. As soon as you change one of the points the path of the fork changes with it.

I'm making an "extension" on the ULM to allow the use of a shorter shock. The ULM position won't change at all. I'm only changing where the shock mounts. You'll see when it's done. Take a look at my pic of the front with the stock Noleen NR-2 in place - notice the extension under the spring? 9.75" i2i.

Nothing to be p-d off about at all. I hope i'm not coming across as such? As far as what you've bought - this is really uncharted territory for me. My swingarm pivot is a bit different from yours, so I could only roughly guess about what will change by how much. I don't want to do that. You're best bet would be to take your measurements with the stock shock in place and record them. Might be worth it to also measure the travel, when completely compressed. You can always sit the bike on it's wheels without the rear shock and move things around to get a good visual of what will change with different shock lengths. Much easier with a helper.

Really, it all depends on what you want to do. In your case, "loosing" 10 mm of shock length (you mention 9 mm "on each end"?, but it doesn't measure as such) will drop your headtube angle. Unless you want to loose rear wheel travel and also slow your steering (is that the right phrase?) then I wouldn't do it. We discussed geometry in our P.M.'s and you're changing it "considerably", IMHO.

You've got a good base of understanding with your moto background - just keep in mind that when it comes to mountain bikes, most people don't alter geometry like this.

jazclrint · « **Reply #8 on:** April 26, 2005, 04:16:05 pm »

Yeah thats what I thought. The rear is going to be lower than the front which is the exact oppiste of what I want. I wanted a little more rear height, to improve the handling. But to make adapters for a mere 3/8" seems much harder than what you've got going. But, a "spacer" for the rear seems much simpler, but even that might be too much of a difference. I've got a concert tomorrow night, and then finals in 2 weeks. Then I'll have some time to play before I head to Australia for the summer. I'll definately post what I find on my end. Nope, you don't seem pushy at all. I just didn't want you to think that I had blown off your advice.
Later,

jazclrint · « **Reply #9 on:** April 29, 2005, 06:51:43 pm »

Well,
Not being sure where to post this info I chose here. The Fox Floats are probablly the worst configured shock for this bike. Just to reitterate I have 2 Fox Float RL AVA's w/Pro Pedal at 7 7/8" length and 2" of shock travel. Quick math says that takes the rear from 4.7" to 5.4" in the rear, and 3.0" to 3.4" in the front. I believe that I would have a lot less of a problem fitting these shocks if they were both shorter, and and just Float Rs (as in minus the Lock out lever). The AVA does not intrude at all, but the diameter of the body makes the front a very tight fit. And the placement of that vavle is just evil! I have made drawings, and handed them to the local machineist to see what he thinks. I will worn you all that the standard adaper will not work for a 7 7/8" shock (if you want to keep the stock length) because the top of the shock wants to be right in the middle of the pivot bolt. And my front design is no where near as beefy as Frankd3000's. And talk about tight tolerences! But it should be light and strong. I will be able to make the lock out work in the front, I think, but I will have to shorten the lever. The front is a MULA 1 design, but smaller, reflecting the limited room I had to work with. I think the AVA is really the way to go with the front end, where it is such a different situation for the shock. The rear is going to be ok. My first design was a standard adapter but it has to be put on the top of the shock because of the way the Fox was designed. The only problem is that it added 5mm of length to the shock. The same as having a 8.5" shock on the rear. So I redisigned it. The adapter will be much stronger, but I wonder if the 2 bolt desing will hold up to the abuse. The bolts would be the only weakness. But, I believe it will make the lock out and air valve easy to get to, and give the proper length. We will see how I did. I too am having a brass sleve made for the bottom shock pivot. I am also going to put a ton of nylonish bushings all the way around. The machineist had a certain material he recommended. That's about it fir now. It should be about a week before parts are done. But tha's ok because the weather is crappy here right now. Later.

jazclrint · « **Reply #10 on:** May 07, 2005, 07:17:58 am »

I got the parts from the machinist yesterday! But I am in the middle of finals so no pics or fitting reports yet. But I am quite excited at the possibilities. All of the aluminum peices, "dextron"? washers, and brass bushings came to $120. No Ti though. He couldn't get a hold of his buddy. I'll keep you all posted.

Frankd3000 · « **Reply #11 on:** May 07, 2005, 04:49:09 pm »

Ah crud. I wish I read this sooner. One other thing to keep an eye out for, Jaz - the width of the lower shock mount ~> lower link. I measured mine up and the link has a 0.900" wide gap. The Noleen NR-2 is about 0.585" wide, while the CC C9 is 0.500", so I used two EXTRA o-rings to make up the difference. Check out my gallery, I updated the pics showing the o-rings and my air valve clearance "issue".

I think you have great shocks to work with, just not the "right" length. You're finding this out now, but you can always find a work-around. Remember, there's nothing that says you can't raise the ride height entirely. If you find that the length of the rear shock will raise the rear height by 1/2", then you can always fabricate to do the same in the front - see where i'm going with this? The advantage is that you gain BB clearnace - a necessity when increasing travel. Just keep it reasonable - raise too much and you'll screw up the geometry with your CrossLink.

Get it together and take some pics and let's see what you have.

Oh yeah - GOOD LUCK with your finals!!!!!!

jazclrint · « **Reply #12 on:** May 07, 2005, 07:53:43 pm »

The Fox is almost as wide as the Noleen, so all I need are the washers with a 1/2" ID (which I had 2 made) to take up the slack. I already cought that, but thanks for the heads up! I have to disagree that you NEED more ride height with more travel. I will set the sag as per the manual (10mm/8mm f/r) Now the advantage of this is that I get to use a softer spring rate in order to take advantage of the extra 1/4" of travel (in the shock). But all my extra travel is in the wheels coming closer to the frame. So this isn't taking complete advantage of the extra travel. If I had given it more thought I might have gone with the extra 3/8" in the rear. I don't know if there is enough room in the front. Because, as I'm sure you know, with more ride height and more travel means you get to run more sag, which lets the wheel "fall" into holes more, and keeps the tire in contact with the ground more which gives you more control, and a better ride. This really is the best way, but takes a lot more thought and trial and error than mine, and I don't concider it a nessesity. But I would definately go with 7.5" Floats next time. They have the same amount of travel and give better clearence for the adapters. Now that I think about it, I don't think there is enough room to make the ride height any more in the fork because of the size of the shock body.
Oh yeah, and all those on the edge of your seats (yeah right), may have to wait even longer. I forgot I have Drill next weekend. I'll do what I can.
Later,

Frankd3000 · « **Reply #13 on:** May 08, 2005, 05:44:11 am »

You're right - I forgot about the whole sag-thing. Not used to that, as it was never discissed when I was into things. Now it seems that it's an important thing to consider. Understandable.

One thought - if you use sag as your judge for your air-pressure setting, aren't you compromising your shock settings? Softer rates result in more sag and vice-versa, right.

Looks like you and I have some "busy time" ahead of us. You're ready to go and so am I. [smiley=nod.gif]

Good luck with it!

jazclrint · « **Reply #14 on:** May 08, 2005, 04:21:12 pm »

I'm pissed! I just spent 2.5 hours writing this big long thing on my opinon of suspention (I type slow), I hit submit and this site lost it. ARRRGGGHH. But, at least you all were spared. ; )
Andrew,
The whole point of setting the air pressure is to set the proper preload, which is determined (atleast as a initial fixed setting, which I prefer to think of it as fixed) by the amount of sag you need to run. Setting the air pressure is the same as tightening your spring. Only with a spring it could be a linear (equal force though out the compression of the spring) or progressive (increasing force as the spring is compressed) spring. And it is a set force. With air, the more you put in, the more spring rate there is. Also air is progressive. So, if you are heavy like me, I set the air pressure for sag, and I have more air, but I'm heavier, so I need more spring rate any way. It is all in the hands of the designers of the shock as to what the spring rate is with a certain psi. But, I have the AVA sytem on the Fox float, which allows me to adjust the sping rate quite a bit (or so the manual says). This is a BIG advantage for setting the fork, much less the whole bike, up.
But I believe your concern stems from me wishing to run more ride height so I can run more sag. Well, concidering that Fox recommends WAY more sag that Proflex says to set the shock up with, and sense there is more travel, and air is a progressive spring, there is little reason for concern over just an extra 5mm of sag, at least in the rear. And with the AVA system, I have no concern. But you should be setting the shock pressure to the sag. That's how you are suppose to do it. So I'm not quite sure how that would be a compromise in settings. Actually now that I think about it Fox recommends 12.7mm of sag on their shocks. My front is supposed to be 10mm, so that is close enough. But if I put 5mm more length in the rear adapter, and hense 5mm more sag to compensate, that would be 13mm of total sag (5500 suppose to be 8mm rear) which is almost perfect. Ah heck. Well, I could have my machinist drill a hole 5mm further up, and then I could switch between the 2 and see the difference. Oh, SOOO much R&D, and so little time.

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Author Topic: Shock length for Carbon (and all?)? (Read 5870 times)