Help! Fork issues!
Discussion
I tried setting up my forks this evening and it didn't go well. Experimentally I found the least poor ride came from about 150psi positive and 120psi negative, at which point it feels relatively plush, but it's still bottoming out very easily.
Based on the info I've gleamed here and in the manual I calculated for my 13.5st riding weight I needed 127.5 positive and 117.5 negative, but the above feels better.
Anyway, on 150/120, the sag is about this much:
And maximum travel (after bouncing up and down on the front hard enough to bottom out I think - certainly felt like it), is about this much:
The sag is about 25mm - seems sensible for a 100mm travel fork, however, as far as I can see it's only actually travelling about 50mm.
Am I being really stupid somewhere?
I emptied all the air out of both chambers, at which point the fork still sat quite high (I assumed the bridge would be almost touching the tyre - just minimal mud clearance left). I refilled the positive first, then turned the bike over and did the negative.
After hours of playing around I double checked the shock pump and, yes, it's psi. The Poploc is off. The rebound is almost 100% fast so it's not packed down. I'm still getting the situation you see in the photos.
I've probably massively misunderstood something and I'm probably making an idiot of myself here, but should a 100mm travel fork not have 100mm of travel? The only thing I can think of is the Shock Pump - it's Halford's own brand, but seems sturdy enough. It does cause the valve to leak a small quantity of air as you unscrew the pump (the reading is about 10-15psi than you originally pumped to if you reapply it), but even adjusting for this doesn't solve it.
Help!
Based on the info I've gleamed here and in the manual I calculated for my 13.5st riding weight I needed 127.5 positive and 117.5 negative, but the above feels better.
Anyway, on 150/120, the sag is about this much:
And maximum travel (after bouncing up and down on the front hard enough to bottom out I think - certainly felt like it), is about this much:
The sag is about 25mm - seems sensible for a 100mm travel fork, however, as far as I can see it's only actually travelling about 50mm.
Am I being really stupid somewhere?
I emptied all the air out of both chambers, at which point the fork still sat quite high (I assumed the bridge would be almost touching the tyre - just minimal mud clearance left). I refilled the positive first, then turned the bike over and did the negative.
After hours of playing around I double checked the shock pump and, yes, it's psi. The Poploc is off. The rebound is almost 100% fast so it's not packed down. I'm still getting the situation you see in the photos.
I've probably massively misunderstood something and I'm probably making an idiot of myself here, but should a 100mm travel fork not have 100mm of travel? The only thing I can think of is the Shock Pump - it's Halford's own brand, but seems sturdy enough. It does cause the valve to leak a small quantity of air as you unscrew the pump (the reading is about 10-15psi than you originally pumped to if you reapply it), but even adjusting for this doesn't solve it.
Help!
Edited by Chris71 on Wednesday 10th September 20:41
RS forks?
I have RS Reba SL's on my HT, and they're only 95mm travel as measured, despite being a 100mm fork. I'm 13.5 stone and I'm currently running 110PSi + and 90PSi - if that's any help? I've gone from 150/130 down in 10PSi increments until I found what I was comfortable with.
I have RS Reba SL's on my HT, and they're only 95mm travel as measured, despite being a 100mm fork. I'm 13.5 stone and I'm currently running 110PSi + and 90PSi - if that's any help? I've gone from 150/130 down in 10PSi increments until I found what I was comfortable with.
Edited by WildCards on Wednesday 10th September 21:45
They are indeed - Reba SLs and the bike is a 2003 Sub 5 if that mnakes any difference.
I'm afraid this is a maximum of about 50mm travel as far as I can see (haven't measured it, but it's waaay short of 100mm).
It turns out the gauge pressure is a red herring - I'm told the air escaping is that in the pump (downstream of the gauge) not that in the fork. Not that it makes any practical difference - I tried pressures down to about 90psi.
The technique I was told to try elsewhere is:
"Empty the negative chamber.
You want about 25-30% sag on a fork - nearer 25 on a 100mm I'd say. So set your strap 25mm above the fork seal and put too much pressure in in the positve chamber - say 150psi. Then get into position on the pedals and over the bar as if you were just about to cruise into some nice singletrack (don't bounce) and get a friend to use the release button on the pump to slowly (repeat slowly) lower you down to where the strap is.
Note the pressure on the pump and put the same pressure in the negative chamber - again assuming the air spring is the same as the Pikes.
If you find it too active drop a little out of the negative chamber. If you find it wants a little more movement on small trail buzz type bumps (think cobbles - or most of Dalby red if you know Dalby) add a little. Around 5 psi, 10 tops either way."
Sounds plausible. I think I'll give it a go when I have some daylight and a willing helper.
I'm afraid this is a maximum of about 50mm travel as far as I can see (haven't measured it, but it's waaay short of 100mm).
It turns out the gauge pressure is a red herring - I'm told the air escaping is that in the pump (downstream of the gauge) not that in the fork. Not that it makes any practical difference - I tried pressures down to about 90psi.
The technique I was told to try elsewhere is:
"Empty the negative chamber.
You want about 25-30% sag on a fork - nearer 25 on a 100mm I'd say. So set your strap 25mm above the fork seal and put too much pressure in in the positve chamber - say 150psi. Then get into position on the pedals and over the bar as if you were just about to cruise into some nice singletrack (don't bounce) and get a friend to use the release button on the pump to slowly (repeat slowly) lower you down to where the strap is.
Note the pressure on the pump and put the same pressure in the negative chamber - again assuming the air spring is the same as the Pikes.
If you find it too active drop a little out of the negative chamber. If you find it wants a little more movement on small trail buzz type bumps (think cobbles - or most of Dalby red if you know Dalby) add a little. Around 5 psi, 10 tops either way."
Sounds plausible. I think I'll give it a go when I have some daylight and a willing helper.
The advice above sounds pretty good.
Note that the forks can be set up with 80mm travel - are you 100% sure they have been set up for 100mm? (i.e. where did you get them from; are they OE forks from a built-up bike or something?)
Other than that, they're brand spanking new so don't expect all the travel straight away until you have a few 100 (rough) miles under your belt.
Having said that, 50mm is very little travel.
You say that the poplock is "off", but have you confirmed that the blue knob it attaches to is fully anticlockwise? The remote could be installed incorrectly and not releasing it all the way back.
Note that the forks can be set up with 80mm travel - are you 100% sure they have been set up for 100mm? (i.e. where did you get them from; are they OE forks from a built-up bike or something?)
Other than that, they're brand spanking new so don't expect all the travel straight away until you have a few 100 (rough) miles under your belt.
Having said that, 50mm is very little travel.
You say that the poplock is "off", but have you confirmed that the blue knob it attaches to is fully anticlockwise? The remote could be installed incorrectly and not releasing it all the way back.
Sounds more like you've put too much air in the fork. You say 'bottoming out' but you're only getting 50mm of travel so how can they? An you're running 40psi more than he above who weighs the same. That's nearly 45% more, it's no great suprise that YOU are not getting a lot of travel. Get a 18-stone bloke to push on them and you'll get the full travel ;-).
I'd get the manual, an nice cup of coffee/tea, take a deep breath and start from scratch.
I'd get the manual, an nice cup of coffee/tea, take a deep breath and start from scratch.
I'm afraid it sounds like there's a bit more to it than that. My 13.5 stone is more than addequate to find a distinct stop at the bottom of the travel, at which point it's barely taking up the sag.
I phoned TFT (top blokes - they didn't supply the forks, but were very happy to advise) and they reckoned it was oil in the lowers.
Merlin who (supplied them) said [of the thousands they've sold] a few have come back with this problem.
Is there anything that can be done? I'm supposed to be leaving for Wales tomorrow afternoon for my one sustained weekend of decent riding this year.
I phoned TFT (top blokes - they didn't supply the forks, but were very happy to advise) and they reckoned it was oil in the lowers.
Merlin who (supplied them) said [of the thousands they've sold] a few have come back with this problem.
Is there anything that can be done? I'm supposed to be leaving for Wales tomorrow afternoon for my one sustained weekend of decent riding this year.
Chris71 said:
My 13.5 stone is more than addequate to find a distinct stop at the bottom of the travel, at which point it's barely taking up the sag.
(
I don't really understand what you're saying there. My 14-stone is more than capable of finding a distinct stop in my 18-stone friends forks but it's not at full travel because his set-up is for a heavier guy. And when fully compressed 'sag' has nothing to do with it. Are you saying that the forks only move about 50mm in total although they 'sag' 25mm when you're sitting on the bike?(
Excess oil in the lowers sounds plausible and easily fixed - an oil change. Shouldn't take long but if you can't do it, finding a competent LBS on short notice might be a problem. It is quite straight forward to do though.
I still think your pressures are too high (ETA) as well.
Edited by mk1fan on Thursday 11th September 12:12
Chris71 said:
I'm afraid it sounds like there's a bit more to it than that. My 13.5 stone is more than addequate to find a distinct stop at the bottom of the travel, at which point it's barely taking up the sag.
I phoned TFT (top blokes - they didn't supply the forks, but were very happy to advise) and they reckoned it was oil in the lowers.
Merlin who (supplied them) said [of the thousands they've sold] a few have come back with this problem.
Is there anything that can be done? I'm supposed to be leaving for Wales tomorrow afternoon for my one sustained weekend of decent riding this year.
Hard to say without actually trying them myself, but it does have all the hallmarks of being set up too hard for you weight, when it bottoms out does it just stop moving or give a jarring "DONK"? You could set the pressure very low to see if the forks will give full travel. Otherwise where in Wales are you heading? If it's in the south I dare say I know a really good LBS in the area you could take them too for a once over. I phoned TFT (top blokes - they didn't supply the forks, but were very happy to advise) and they reckoned it was oil in the lowers.
Merlin who (supplied them) said [of the thousands they've sold] a few have come back with this problem.
Is there anything that can be done? I'm supposed to be leaving for Wales tomorrow afternoon for my one sustained weekend of decent riding this year.
It's a definite, mechanical-sounding 'donk'.
Both TFT and Merlin are aware of the problem with a small number of Rebas apparently.
It even happens with no air in whatsoever, so it can't be over-pressurised.
Looks like I've found a sort of solution - Merlin will take the Rebas back once they're removed and give me a refund. Meanwhile a friendly local bike shop have offered me a deal on some Revelations and last-minute fitting.
Sounds like the best option - no one can service them at such short notice (I'm leaving in about 24 hours!) and attempting anything myself could prevent me from getting a refund if it doesn't work.
Both TFT and Merlin are aware of the problem with a small number of Rebas apparently.
It even happens with no air in whatsoever, so it can't be over-pressurised.
Looks like I've found a sort of solution - Merlin will take the Rebas back once they're removed and give me a refund. Meanwhile a friendly local bike shop have offered me a deal on some Revelations and last-minute fitting.
Sounds like the best option - no one can service them at such short notice (I'm leaving in about 24 hours!) and attempting anything myself could prevent me from getting a refund if it doesn't work.
I like Whytes at Glyngorgg (Afan). The optional 'Black' loop is a nice - and not as daunting as the label implies. I also Like the Penhydd at Afan and the final descent of the Wall.
CwmCarn is just one official trail but you can do a single trip on the uplift to do the DH course which is very good - and very rideable.
CwmCarn is just one official trail but you can do a single trip on the uplift to do the DH course which is very good - and very rideable.
I loved the Penhydd so much I just did that one twice at Afan! Apart from the first climb (which is hardly lung bursting by Welsh standards) there just seems to be so much downhill for so little climbing.
Cwmcarn was actually harder work than I remember it being, but the top bit of the XC trail (near the freeride area) and the epic final descent make it allo worth while. It's got a bit more exciting since I was last there as some of the surface has washed out a bit more leaving it rockier. The final bits that were insanely fast previously are now just very fast.
I contemplated trying the downhill, but my mate I was riding with had injured himself at Afan and called it a day when we were half way round Cwmcarn. It would have seemed a little unfair to leave him sat int he car when we needed to get back. Plus everyone getting on the uplift seemed to have full face helmets and very serious big hit bikes.
Speaking of bikes... The Sub 5 works fantastically with the Revelation. The only time the fork length became an issue was on sustained steep climbs (and then I just wound it down). The rest of the time the increased travel and plush action more than made up for that. The bike will now just float over stuff that you had to be covering the brake for last time. Even on 130mm I think it handles better than before and its agility isn't dramatically effected. Quite pleased with the way things worked out.
Cwmcarn was actually harder work than I remember it being, but the top bit of the XC trail (near the freeride area) and the epic final descent make it allo worth while. It's got a bit more exciting since I was last there as some of the surface has washed out a bit more leaving it rockier. The final bits that were insanely fast previously are now just very fast.
I contemplated trying the downhill, but my mate I was riding with had injured himself at Afan and called it a day when we were half way round Cwmcarn. It would have seemed a little unfair to leave him sat int he car when we needed to get back. Plus everyone getting on the uplift seemed to have full face helmets and very serious big hit bikes.
Speaking of bikes... The Sub 5 works fantastically with the Revelation. The only time the fork length became an issue was on sustained steep climbs (and then I just wound it down). The rest of the time the increased travel and plush action more than made up for that. The bike will now just float over stuff that you had to be covering the brake for last time. Even on 130mm I think it handles better than before and its agility isn't dramatically effected. Quite pleased with the way things worked out.
Ironically (I think I'm using the phrase correctly), I serviced my Talas forks on Saturday and over filled the Talas unit with oil. The book only refered to Float units and needing 35ml in the spring side. Which I duely did. But I was only getting 85mm of the 125mm of travel. Spoke to Mojo today and Talas units only have 15ml in them. Opps. Haven't riden on them yet so, luckily, a quick drain and re fill is all that is needed.
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