All the gears, no ideas
At the beginning of the year I started a custom build project ending up in June with a 2005 Marin Attack Train Frame, full Shimano XT groupset and a nice set on Rockshox Revelation forks up front all for little over a £1000 (the wonders of eBay).
After a few summer rides the bike was spot on, then, a week ago whilst riding home I was on the biggest chainring (mega9) and biggest sprocket when the chain began trying to skip off the chainring down onto the middle ring. I had a good look at the setup and found the front mech needed tightening up and aligning. I thought I’d cracked it. Oh no. Took the bike out and tried it out. As I put my weight through the crank the chain skipped again resulting in me over the handlebars, oh how my wife laughed.
Now, no how much tweaking with the gears (followed Shimano’s website to the letter of the law) I cannot seem to prevent it trying to skip. When I have the chain on the big sprocket and chainring and turn the crank backwards the chain skips down 4 sprockets, should this be common? I’m now starting to question whether the BB is the correct one.
Also, when I’m on the smallest chainring and smallest sprocket the chain runs over the plate which connects the outer plate of the front mech to the inner one, can this be correct as the mech cannot go any lower?
Next port of call is the local bike shop — is there something obvious I am missing before I do?
The obvious thing you are overlooking is your gear selection while riding!
Although your choice should always be long enough to allow you to select the biggest front with biggest rear gear, in reality you shouldn’t be trying to run this extreme gear, the same is true of the small front, small rear combo. The angled chainline created by trying to run these gears often causes the problems you are experiencing.
Accepted good practice dictates you should be running small front with the larger half of the rear cassette, middle front with every rear gear and finally large front with the smaller half of the rear cassette.
The gears placed “out of bounds” are duplicated elsewhere in the range so you still retain a full efficient range of gear ratios working on an
optimised chainline and with decent chain tension which besides giving smoother operation will extend the life of the drivetrain components.
If you really do feel a need to run the unrecommended gear ratios then every part of the drivetrain will have to be set up perfectly and be in pristine condition (you didn’t say whether your Ebay bargains were new or used?) which is a job for a professional cycle mechanic, even then there is no guarantee smooth operating can be achieved.
Having recently completed an upgrade on my Marin full susser, I decided to fit all my old bits onto a hardtail for use as a commuter/play bike; one of the old components was a set of 2004 Marzocchi Comp-airs. The hardtail the frame that I have fitted them to is a size small Scott Yecora that I bought relatively cheaply but I am concerned that the mx comps have too much travel for such a small frame and have slackened the head angle too much. Any thoughts?
Sizing of the Scott Yecora is not really relevant. The issue is whether or not the frame has been designed with a suspension fork in mind and the appropriate geometry changes have been taken into consideration. Luckily the Yecoras of recent years originally came with suspension forks as standard. Your Marzocchis will be slightly taller overall than the original fit fork giving a more relaxed head angle, increasing stability but decreasing slow speed response. Personal preference always dictates what is ideal in terms of handling so only you can decide if you like the end result. Give it a try!
I recently bought some Pace RC41 Fighter forks. I am very happy with my choice and they are a lot better than I will ever be.
My reason in writing to you is to let you know that I no problem transferring my original M4 Hope brakes onto the forks. Recently and I also fitted a new set of wheels with Chris King disc hubs with everything working perfectly. My problem has come with the upgrade of my brakes to Mono 6Ti’s. My back brake is fine but the front ISO disc mount for the caliper will not fit between the fork and the disc as there is insufficient clearance. I cannot be the only person trying this combination of items and with me present, my shop called both Pace & Hope and both of them just told us that it was an incompatibility issue and to “Try another combination”. You would think Pace/Hope would make potential buyers aware of this issue on their respective websites or at least issue warnings to Reps and distributors or am I being naïve?
Maybe you could let others know of this issue to avoid buying expensive items that will not work together. Undeterred by this, I have managed to find a local engineering firm who is going to machine me a new ISO mount to allow my brakes to work. I’m damned if I’m going to spend £500+ for the forks and £350+ for my brakes to be told “Try another combination”. I don’t care about the cost of the machining. It ‘ s the principle of it.
I hope this helps others who may not have the luck/good fortune to know a good engineering firm to help them out. If anyone wants to know what is needed to be done to expediate this, I would be happy to answer any emails sent to you and show them what is required.
Thanks for a great Magazine.
Thankfully compatibility problems are not as common as they used to be.
There are standards set for the frame and fork mounts as there is for the 6 bolt fixing pattern on hubs. These advisory standards purposely allow for subtle variations to be incorporated into the manufacture of the forks, hubs and frames. A World Cup downhill bike running 203mm discs benefits from beefier disc mounts whereas the World Cup XC bike running a 140/160mm disc combo wants the minimalist approach.
Rather than falling foul of unco-operative manufacturers it is your
“unusual” mix of components that unfortunately has caused an issue in this instance.
Fitting Hope’s heavy duty downhill brake to Pace’s trail/all mountain fork is a combination that neither Company envisaged.
For most buyers the more appropriate brake from Hope would be the Mono M4, which you already know, works fine.
The main item you have a problem with is the Hope Ti 6 mounting bracket
which is “oversize” for a reason, to meet the demands of pro downhillers and give a flex free fitting on today’s range of downhill forks, all of which it fits!
Manufacturer’s can give guidelines with regards to suitable applications but it becomes a logistical nightmare to cover every possible combination of fork and brake (and hub as this affects the discs positioning).
The best course of action is to check before purchase as to whether your chosen components are compatible.
Hi mbr, I’ve recently bought a pair of new wheels for my bike. With my old wheels I used Nutrak Butyl LightWeight tubes (176g) and Panaracer Fire XC Pro tires but the problem is I always got punchers. But every time I got puncher I had to get my dad to take my tires off to fix the it, because of my rims (Sun black eye rims) and my dad struggled to get my tires off! So every time I got a puncher I had to wait for my dad to get home from work. So when I got my new wheels I started to use slime inner tubes (340g) which are great but they are a lot heavier so I don’t get the benefit of my new wheels. The problem with the nutrak tubes is the puncture and pop very easily so I couldn’t use those. Please can you recommend any tires or tubes, which are light enough to benefit from my new wheels without getting punctures everyday! Please help me to get out of my misery because I’m 13 and I have to got to school and do homework so I haven’t really got time to fix punctures! Thank you for your time I hope you can help me.
The rim, tube, tyre combo you’re using shouldn’t be causing any problems, as they are all “pukka” parts.
You haven’t stated what “type” of recurring puncture you are getting – pinch flats or holed tubes from objects piercing through the tire?
If it is “pinch” flats, make sure your tubes are inflated fully, also check the rim tapes in good condition and if it is of the “plastic” variety that there are no sharp edges or better still replace with a good self adhesive type of tape (cloth or pvc). While you’re at it, inspect the rim’s valve hole for sharp edges and the same goes for the spoke ends and rim joint. If all seems OK turn your attention onto the tyre. Besides the usual feel inside for anything protruding through, carefully inspect the beading, sidewalls and main carcass for any tears or small holes. If you find any throw the tyre and replace with a new one.
If everything checks out but you still suffer from punctures then you’ll have to consider fitting a heavier i.e. thicker walled tyre to tube.
If you are trying to stop something sticking into a tube you need more rubber as a barrier.
If you are trying to stop a tube being “pinched” by the rim when hitting an object hard you need more rubber to cushion the blow. That’s why DH tyres and tubes are so heavy – not by choice but by necessity (although tubeless tyres partly addresses these issues!).
If you do decide to buy a different tyre – take along your wheel with you and make sure you are able to fit your new tyre onto the rim easily, preferably without tyre levers. At least that way you will not have to wait for your Dad to mend your punctures.
I have not recommended a specific tyre as the range is huge, you are better putting the staff at your local shop on the spot and asking them what they use, which of course will be relevant to local riding conditions.