i bought a pair of carbon bars for ny mtb, then found out there 40mm too wide, any one know if its safe or even possible to cut them down, carbon fibre is funny stuff safety is most important .

I need to get a crabon steerer cut – no way I’m doing it myself! The angle I always get on an alu one is less than amusing – and that’s using a cutting guide :/

I’ve been advised the crabon specific hacksaw blades can make even more of a mess than regular ones.

Use an abrasive hacksaw blade and don’t expose any part of yourself to the dust or fibres.

I thought the video on this website on cutting and sanding carbon fibre componets was quite good. Whilst it promotes the products they sell, interestingly they show perfectly good cuts being achieved with an ordinary hacksaw blade instead of the abrasive type blade.

good point about the carbon dust, i may just put old bars back on & ebay the new ones . thanks for everyones reponce .

Any fine blade will do. Wear a mask and gloves. Use masking tape to draw the cut line on.

I took mine into the LBS who chopped them down for a tenner…

For my carbon seat post I bought a cheap mitre box from screwfix direct (about a fiver) and a cheap 32 tooth per inch hacksaw blade. I sawed it off outside, the dust drops to the ground so doesn’t go airborne so you’re OK. Cut through it like a hot knife through butter, and left a really clean edge. I used a piece of fine sandpaper on a flat surface and rubbed the cut edge at 45 degrees to take off the sharp edge and chamfer the edge slightly. A professional job done in about one minute.

just more the grips 20 mm each inboard?

As above a fine-toothed hacksaw goes through it like butter. Obv don’t inhale the dust

What wobbliscott says ^^^^. If you want you can seal the cut edges with polyester resin or even nail polish.

Old pair of lock ons as a guide and a hacksaw or grinder with a fine blade (I only use the grinder option at work under a large industrial fan heater with a vac).

It’s perfectly reasonable to cut your bars down. I didn’t want to put the dust into my vacuum so cut them outside with a some water running over the cut. One opinion here. Skip to 17.40 to for advice on cutting carbon[video]https://www.youtube.com/watch?v=EZbg5hCRyvs[/video]

I used a pipe cutter on bars. And a normal hacksaw on a steerer.
Can’t believe no one has suggested just getting used to the width! What is STW coming to? 🙂

I bought X-Tools saw guide £14.99 CRC for cutting bars, makes life easier, bought a wad of fine blades recommended for cutting carbon from screwfix for pennies.

as above. you need something to give you a guide aso you get them straight and a fine bladed hacksaw. If you aren’t confident yourself then take it to a bike shop.

It isn’t something to be scared of. Same with steerers, I’ve always just cut them. Carbon composites aren’t some terrifyingly complicated material.

As for the dust, it will be minimal. Do it somewhere with a bit of ventilation. It is a one off, you are not handking industrial quantities of the stuff.

If you have any old lock-on grips, the lock pieces are perfect saw guides. There’s things you can do to cut dust- even masking tape around the bar will hold most of it- but tbh I just do it outside, if I worked on a production line cutting bars I’d feel different I’m sure.

Seriously, the dust doesn’t go airborne, it’s not that fine, so just breathe gently, keep your face well away and you’ll be fine. If you’re that bothered just pull your T-shirt neck up above your nose or set your vacuum cleaner up with the hose nozzle close to suck up all the cuttings. You’re breathing in far more toxic crap riding your bike along a busy road anyway.

Use masking tape at the cut to prevent splintering.

If you’ve got an old set of lock on grips knocking about you can use the locks as a guide.

As for the dust, it will be minimal. Do it somewhere with a bit of ventilation. It is a one off, you are not handking industrial quantities of the stuff.

This 1000x .I’ve always used a saw guide and whatever blade is in my hacksaw. As it’s something I do very occasionally it’s never occurred to me there could be a risk, and there isn’t IMHO.

I’ve always measured and put a slight nick in a few places around the circumference at the right distance from the end, then gone round with a normal hacksaw joining them up and then cutting all the way through. Sandpaper and sanding block to smooth off the edges.

AFAIK I’m not dead yet.

It’s a very easy job, much easier to cut carbon steerers and bars than alu.

The dust is heavy and just drops into the bar or to the floor, and there’s hardly any of it. It’s not like plaster dust which goes everywhere.

For steerer cuts, I use an old stem clamped in the right place and use the edge of the stem as a guide. For bars the above suggestion of a locking grip collar is good. Maybe use two with a saw blade gap width as a guide.

Mtfu 😉

PS, have you tried the wider bars first for a few rides? I find them great whereas I was cynical at first and it takes a couple of ride to get used to them. I now use 750mm for xc race and 780 for the fun bikes.

I’d ride with them before cutting them, chances are after a couple of weeks you’ll wonder how you coped with narrower bars.

Some outfit called NASA say this about carbon fibre

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150012180.pdf

but they dont say anything about handlebars though.

masking tape around the cut to stop fibre delamination

water for smoothing the cut and damping the dust down

we use a brand new 32tpi steel hacksaw blade each time (you don’t want to snag fibre on damaged teeth, or introduce contaminants such as aluminium alloy and steel into the cut area

the carbon fibre blades are messy and make a wide rough cut (we were told not to use carbon blades by one of the largest manufacturers)

then finish with fine grade wet and dry

1. Measure the bar to the width you want. Only do this once before making the cut.

2. Put your right index finger at the point to cut. Then swap to your left hand so when you are gripping the bar the outside of your index finger is where you want to cut.

3. When you realize you haven’t got a saw close enough to reach, grab the wood saw that`s nearest. Next hold the bars tight to the front of your thigh and begin cutting.

4. Using the edge of your index finger as a guide, draw the saw back slowly to begin the cut, then, when you think the time is right thrust it forward taking most of the skin off your right index finger and cutting slightly through your jeans and into your knee.

5. Repeat step 4 until you have cut right through the bars.

6. Stand back and admire your handy work, whilst trying not to pass out from the blood loss.

paton – Member
Some outfit called NASA say this about carbon fibre

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150012180.pdf

but they dont say anything about handlebars though.

“Consistently, there were no significant pulmonary function changes or evidence of fibrosis in
either the pitch or PAN-based carbon fibers. The author concluded that unlike the silica-based
asbestos fibers, pitch-based carbon fibers do not cause pulmonary fibrosis. Based on the
studies it appears that toxicity of respirable, raw carbon fibers and composite dust is
substantially different from well-known carcinogenic effects such as asbestos and man-made
mineral fibers. The toxic hazards of carbon fibers and dust rank significantly lower compared
with the crystalline silica dusts.”

Just cut it with a hacksaw and get on with your life.

Struggle to think of any handlebar on the market that’s 40mm too wide.

I’d keep them the width they are 🙂

Masking tape wrapped tightly to prevent splintering, clearly marked line to cut to, and standard metal hacksaw blade (can’t remember the tpi but when I looked up instructions for this the only manufacturer ones specified the same tpi as my metal hacksaw blade).

Of course, if you can’t cut straight, get someone else to do it for you. You could use an old set of lock on collars as a guide. Goes without saying that measuring is quite important.

I tend to use a dust mask, but I wouldn’t go out and buy one for the job if I had none in. I don’t think breathing loads of dust in is a good idea in general so try and avoid it – but I don’t think it’s asbestos like or anything.

When cutting carbon I wear an NBC suit and respirator in a hermetically sealed room, can’t be too careful.