alexk_il

I'm converting my vintage MTB with into a frankencross commuting bike - drop bars, granny gears, 659b x 2.2“ tires, panniers, carrying laptop, clothes, etc. The total weight of the loaded bike is roughly 11kg without the loaf.

I unsuccessfully tried to use a low cost carbon fork on the bike, got the refund and started to look for a replacement. I liked how the bike hadled with that fork, too bad it couldn't keep the wheel straight all the time.
Carbon fork dropout problems

Unfortunately, there aren't many quality options in the UK for QR forks with A2C 445mm and straight steerer of 300mm. These numbers were given to me by my bike fitter, no reason for me to question them.

I can still use the original old Manitou suspension fork (around 2.4kg) and having little options is making me confused.

Q1: Surly ECR might fit the bill, but it's 1.4kg of weight, plus it's ugly, IMO. Does it make sense to switch from a suspension fork to a heavy rigid one? Are the benefits marginal?

Q2: There is a lot of relatively light aluminium forks that might fit (no name brands, Kinesis, maybe a few other options). Assuming they work as expected, will they give a good quality ride on 2.2“ tires or should I just keep the heavy suspension fork instead?

Here is the bike with the problematic carbon fork. It's rideable, but requires to resit the wheel once in a while.




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veganbikes

I wouldn't buy cheap carbon forks. Get something decent This would probably fit the bill quite nicely https://mrpbike.com/products/rock-solid-carbon and have seen it for sale at UK shops. MRP used to be White Brothers and has been well known for quality stuff for a long time.

Q1: It is a fine fork would work well and great for touring and mounting racks and such. If the suspension fork works and you aren't needing to mount racks or anything I would just keep that though but if not Surly forks are great.

Q2: You are already having issues with cheap no-name stuff don't buy more expecting different results. A good aluminum fork is not going to be as comfortable as the other options would stick with suspension, steel or carbon.

Eric F

Running 2.2 tires, I am doubtful you would notice any ride quality difference between rigid fork materials.

Clyde1820

A little heavy (if your 3lbs mark is too muvch), but Jones Bicycles might have one that you might like the look of.

Plus LWB Unicrown, from Jones Bicycles -- 450mm A2C, 1-1/8" 350mm steerer, 150x15mm thru-axle, chromoly steel, 1535 gr (3 lbs 6 oz).

https://www.jonesbikes.com/unicrown-fork-for-plus-lwb/

t2p

ouch - 2.4 kg Manitou suspension fork ?

not related to the fork ... consider a zero offset seatpost - could have problems with the seat moved up as far as it is the picture you provided

alexk_il

Thanks. Hard to find the specs for the MRP, some sites show the steerer length to be 250mm, it's shorter than what my bike fitter measured for me.

I already have a pair of QR wheels. Don't think converting them to 15mm thru axle is either easy or cheap.

alexk_il

Can you please elaborate on what problems I could have with this seat moved as far as it is now?

veganbikes

I would check with MRP, I am unsure and don't have one physically to measure them.

Most saddles have a min and max setback so they have proper support and aren't putting too much stress on only one part of the rails.

Bike Gremlin

For a front disc brake, the "thru axle" design solves the problem of the brake trying to pull the wheel out of the dropout.
Also, it helps with the wheel's alignment when mounting it.

So, in this case, I'd look for a thru-axle rigid fork - with the axle-to-crown length that compensates for a suspension fork length. Note that the thru axle mount will also require a new hub - either via a completely new wheel, or by reusing the existing rim with a new hub and very likely new spokes as well (depending on the new hub's flange diameter basically).

Surly Krampus fork looks like a decent solution.

alexk_il

I didn't have this issue with the original old suspension fork and my 100mm wheel. I like your idea and might try it, but only after I find that all other options fail. There is always an option to put the old suspension fork back and make the note to myself to get it done right with my next project if it comes to that.

At the moment, my guts tell me to find a good quality used pre-cut QR rigid fork with an alloy steerer and use a handlebar stem riser to get the steerer length I need. Should be cheaper than relacing the wheel and getting a top quality modern fork. Really hope it will work

Andrew R Stewart 

Moving the seat far forward opens up the angle between one's legs and their torso. This affects both the power you can apply to the pedals and the ability to use one's hips to maneuver the bike. With the bars so high up and the stem so short I will speculate that the seat forward is an attempt to reduce the stretch your arms need to reach the bars. As long as you are happy with how this feels this is not wrong. However, many riders find that having their hips set back behind their feet, by more than your position seems to have, aids their riding with efficiency, increases the ability for their core muscles to support their upper body weight and to enhance their handling/steering. When I see the style of fit that your bikes shows I think that the length of the top tube is too long for the rider's torso/arm combo. This is why some bikes have smaller wheels, to allow the shortening of the top tube without ending up with one's feet contact the front wheel. Andy

alexk_il

I actually don't remember the seat being pushed that far forward by the bike fitter; also can't imagine it moving forward under the load when I ride it. Strange...The bike feels good though, a bit twitchy as expected, a bit too high, but nothing that kills the joy of riding it.

You are kind of correct, the frame turned out to be way too large for me after converting it to drop bars. The combined length of the stem length and bars reach was reduced a lot, I'm currently on the 70mm bar and 40mm stem, 110 mm in total. Also the stem was raised by another 50-60mm, don't remember the measurements of the old fork.

The fitting session however started with handlebar removed, the position of the seat was chosen without any reference to the bike length. This advanced forward seat position doesn't make a lot of sense to me now, though the bike feels comfy. I'm confused now, I will doublecheck it's position and compare it to the notes I received from the fitting session.

Andrew R Stewart 

I didn't catch the converted MtB to drop bar aspect initially. No wonder the reach is long.

Are there other flexibility, injury arthritic issues? Andy

sweeks

Could there be a problem with tubular rails collapsing (if rails are tubular)?

alexk_il

All seems to be correct, the saddle setback is 2.5cm.

Ex-fencer here with a couple of abused muscles/tendons. They used to get inflammed after unnecessary quick (out of saddle) race up a steep hill, though granny gears and slowing down solved that problem now.

Andrew R Stewart 

As example my BB center to saddle top (with 170 arms) is about 67.5cm and my saddle set back is about 45mm. I'm 5'6" tall. When i was younger i had less set back but have found a bit more rearward a saddle works better for me. I still spin pretty well, always did.

Fencing- I've know a few people who practice at that. They could be pretty intense and focused. Guess you need to be in a sport who's competitions might only last a few seconds. Andy

t2p

grumpus

I'm wondering why you're using a drop handlebar with so much stack - certainly not for the aero tuck. I'd have thought a butterfly handlebar would be more appropriate for that sort of setup.

alexk_il

I'm learning while building the bike, I prefer this hobby over Netflix. Anyway, I didn't know what butterfly bar was when I started the project.

veganbikes

I sometimes watch Netlifx or similar while working on bikes, they don't have to be mutually exclusive.

t2p

exposed steerer length (or extension ?) is greater than the length of the steerer length inside the head tube ... that’s not a good thing

consider a different stem - riser stem / stem with a greater angle (whatever) to increase height

alexk_il

I know it's not ideal, that's why I call my bike a "franken-cross".

Anyway, one of the goals of this project for me is to learn, so can you maybe explain why exactly this is not a good thing on a franken-bike? Any safety issues?

SoSmellyAir

Your steerer extension(s) are nowhere near as bad as this person's:
Bike Forums - View Single Post - Cannondale Bottom Bracket for Quick 4

Almost all bikes specify the maximum total height of headset spacers installed below the stem. This total height corresponds to a length of the steerer which the manufacturer of the bike (or fork) is comfortably certain would withstand normal riding conditions. By using an extender, you are likely exceeding that length, thus increasing the leverage through which you apply any force to the steerer.

veganbikes

Just so folks are aware that was Sheldon Brown 's bike. He was certainly a master mechanic and that fork was more than likely a steel steerer tube just FYI. He is sorely missed!

Darth Lefty 

I think you need a Fargo