Rear Shock Upgrade

modm3
modm3 Posts: 7
edited September 2008 in MTB workshop & tech
A quick question for the techies.

I've had a root through the search function, but I hope I have a legitimate question here.
I have a Carrera Banshee and it has an X-Fusion Glyde rear shock on it - pants, but that's what it's got. Anyhow, the frame says it has "6 inch" travel, I'm not so sure the shock is providing it though. I'm a big guy, 112KG (slowly dropping ahem !) and pretty tall to go with it, so when sitting on the bike I'm probbaly giving 50+% sag, which means I'm not really getting the benefit of the shock that I could. I find it abrupt and lacking progression or control.
Finally to the question......can I put in a slightly longer shock to maybe make use of the frame design that supposed to offer 6" travel and obviously at the same time to allow the adjustability and control more suited to my size. (or just put a stiffer spring in there)

This would mean that the rear of the bike would rise slightly, maybe not such a bad thing ason a local trail I I was constantly bashing my pedals off rocks which were placed on the sides of the traill, which surely cannot be normal ?

Any input appreciated.

Comments

  • nicklouse
    nicklouse Posts: 50,675
    no. the shock need to be the same length and stroke.

    it sounds like either you need to fit the correct weight spring to give the required sag. or increase the air pressure to do the same (sorry dont know it the shock is air or coil)

    If you were to replace the shock again you would have to get the correct spring/set the air.

    No one issue could be after fitting a stronger spring the rebound could be too fast, if the shock has rebound adjustability then adjust it, if not then it will need sending away for the rebound circuits to be modified.

    there are links in the tech links sticky above to a spring calculator, put in the info ad you will get the spring weight/strength you need.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • I think that the shock in question is coil sprung (see http://www.chainreactioncycles.com/Mode ... elID=21840 ) If so the best solution is as above and get a heavier spring. In the mean time you could wind the preload up using the spring adjusting collar. This will not increase the spring rate but it will remove some of the sag. I repeat adjusting the spring preload is not the solution as a big fella needs a big spring :wink:
  • nicklouse
    nicklouse Posts: 50,675
    Just be careful you do not add too much, as you can then get a situation where the coil binds. All the coils touch and this can cause the spring to snap.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Thanks for the replies. It is that coil shock. It has some degree of rebound adjustment, which might help if I stiffen up the compression preload - but as mentioned, binding can become an issue. I need to more accuratley measure the sag as I'm basing it on the fact that the bike does not appear to give me the 6" of travel promised...... Also I think it already has the heavy spring in there - 750, maybe I'm expecting too much from a cheap shock, the bike is fine for fast trails and XC although VERY heavy, but for real rough stuff the backend is all over the place. Maybe I'll just lay off the pies ! :wink:
  • nicklouse
    nicklouse Posts: 50,675
    the 750 spring is actually neither light or heavy. it all depends on the suspension ratios.
    IE. shock stroke to rear travel. do you have this info?
    as it will give you the info you need for the correct spring weight for you.

    shock stroke? sus travel? and your weight in riding gear.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • supersonic
    supersonic Posts: 82,708
    Plus the 6 inch travel advertised is at full compression, probably dropping off a cliff! It is not something you want to be achieving often. I do understand your queries though, so as nick says, more info on the shock would be good.
  • Shock is 50mm travel, 190mm length and rear travel is supposed to be 6" - 150mm on a 4 bar link. It's coming in around the 800lb mark, which is a bit stiffer than what I have installed. My concern for not getting the 6" travel fully, was that I have been bottoming out the shock without the big drops. There's a 2 foot'ish drop from the front step of the house to flat and it bottoms out there, I'm also having issues with a lot of pedal and crank arm strikes, need a new set of pedals already after only 10 rides - get replaceable studs this time.
    From the TF site, I don't think I need to replace the spring, as my 112kg is dropping, so the spring weight required will lessen. I've turned the compression ring down the max reccomended by x-fusion, 2 turns and it does seem better than it was, the bike is not sinking the moment I sit on it. Not ridden it in anger, so hopefully tomorrow will get to try it out.
  • nicklouse
    nicklouse Posts: 50,675
    when you are on the bike in normal riding gear and position the rear should sag 25% minimum.

    Pedal strikes is down to rider error, you can not pedal all the time.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Thanks for the advice guys.
    When I get fitter my average traveling speed will increase, which will mean I'll be able to freewheel a bit more, I have to pedal most of the time now, as otherwise I risk coming to a stop on some of the trails I do be on........ :oops: Normally have a 250 2-stroke between the legs to get me out of trouble :D