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Increasing stroke length
I have my eye on upgrading the septune shock on my 05 Stumpy 120.
It's a 7.5 x 1.75, but I can only find a 7.5 x 2.00 for a replacement (Fox float)
Will the extra .25 inch stroke make much/any difference to the fit or geometry etc
I recently updated my fork to one with 140mm travel from the previous 130mm if this has any relevence to the answer.
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As you have stated you have grown 10 mm in the front (A bold move, good on you)
From my experience you should be easly able to take the extra 25 mm in the rear.
Just make sure you keep the front firmer than usual whilst also making sure your rear has at least 25% sag.
Hope this helps
Pikey
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Don't worry what other people are thinking,
because most of the time their not.
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Hi Andy,
from what I have read on this subject going for a longer stroke length could set you up for some frame clearance issues .
When the manufacturer designed the frame they would of determined compression ratios to give the amount of wheel travel with the original stroke length.
By increasing the stroke length without increasing the eye to eye length you may well exceed the clearance tolerances depending on the linkage design SP should not be a problem but multi pivot , Horst link or rocker design may be a problem.
What you are doing is enabling the suspension to compress more than the static position designed.
This small amount may well not be an issue with your frame but I would suggest doing some fine measurements first.
Support the frame in a stand with the shock installed then removed adding the increased amount then follow its travel path to be sure you have full clearance and are not impinging on and linkage or frame parts.
As for geo at a guess you will be increasing your BB hight and slightly changing your head angle which will change the feel of the bike but it maybe to small to tell any real difference.
Better be safe than sorry
good luck
Andy,
It's the same eye to eye length so it will not effect to geometry. however you may find the extra .25mm means that your frame will become the bump stop with either the linkage bashing out before the shock reaches full compression or the rear tyre hitting you up the bum. This will not be good for the frame.
You may get away with it. If you can install the shock without a spring and cycle the wheel through its full travel to make sure nothing is hitting before you lay down your money
Hey Andy, I remember seeing a lot on the net about this when researching for my bike. I just did a quick search and come up with this link http://forums.mtbr.com/showthread.php?p=2850559&...
There is quite a few pages just on this post alone and I'm sure there are more out there.
PS. If you log in there are pictures posted as well.
Cheers
Brian
Very helpful
It seems the RP23 is a good replacement for the Triad or Septune, but forum concensus is divided on whether frame clearance will be an issue.
Previously, I cracked and replaced the puny stock linkage plate with a beefy BETD plate that allows for 120mm or 150mm rear travel by using 2 mounting points - I'd include a photo but I'm a techno muppet.
A link is below - the linkage plate is the Specialized Enduro 02 to 04 Linkage
4th down (in blue)
http://www.betd.co.uk/items.asp?CategoryID=48&Na...
If I attach the 15mm longer stroke shock to the 150mm mounting point, will this solve the frame clearance issues?
I love this sort of thing...
First up the extra stroke of a quarter inch is does not translate to 25mm or 0.25 mm. It's about 6mm. And as mentioned pop your bike in a stand and start running about with the measuring tape.
Best to dump all the air from the existing shock, fully compress it and look for how close items like tyre to seat and swingarm to frame etc get when compressed. Then add 6mm. If there is no clash, not even a little bit of a chance of conflict, then all will be good.
The new link looks good so play about with different settings.
Many people will disagree with me on my opinion that Specialized of all companies insist on custom this and unique that and I reckon it's a ploy to force the customer to only buy from them. It's true that one should not muck about too much with extending travel and trying to achieve more and more from one's bike however stuff does wear out and it's preferable to just go and buy a replacement rather than find an odd size. The 200mm X 50mm is possibly the most common size.
For what it's worth my faithful old Trek Liquid had an odd size shock so I replaced it with the closest size available and aside from the inevitable difference of a new part the bike rides the same.
Also don't forget that an air shock has a progressive spring rate by it's very nature so unless you tend to run a lot of sag, ride really hard and bottom out a lot, then I highly doubt you'd have problems. Keep in mind that there is a massive difference between using all of one's available travel and bottom out. As someone else mentioned, the eye to eye is the important one.
In summary mate your new shock will work a treat and your bike will ride better for it.