I’ve had wheel flex before, the Fulcrum 7s on my old CAAD9 would flex into the brakes when I was out of the saddle. Some more tension on the spokes sorted it.

The Shimano RS11s on my Synapse now do the same. I’ve already tensioned them a bit extra, and I run my brake pads quite far apart anyway, but it takes little or no effort out of the saddle to make the rims rub off the brakes.

Before I damage something by constantly adding tension to the spokes, is there any chance this could be a frame flex issue? Anyone else had any experience with this?

Has it only just started happening – which I’m guessing it is from the way you’ve worded your post? Or is it a new or fairly new bike?

Best thing would be to try some other wheels in the frame?

Unless your putting more power throught the frane than Peter Sagan, i’m going to guess it’s the wheels.

Yeah, fairly new, today’s was the first ride where I knew everything wad tight/true/adjusted etc.

Thedoctor – very succinctly put, I’ll maybe persist with the spoke tension!

Adding tension doesn’t make a stiffer wheel, so I’d stop that right away!

Check the bearings are ok in the hubs

Adding tension doesn’t make a stiffer wheel, so I’d stop that right away!

As shown here, I didn’t believe it so tried it out and got very very similar results!

very, very unlikely to be the frame ….

Bugger. So not the frame and not spoke tension then.

Bearings are free of play, rear (shimano) QR is tight and brakes are aligned and pads set relatively far from the rim.

Therefore… I need to lose some weight (because it’s not my awesome power output that’s doing it…) or need new wheels.

Every road bike I’ve ridden will do this. Wheels will always flex a few mm and unless your frame is very rigid BB sway when climbing stood up leads to rear end twist so the alignment of brake and axle shifts a little. Your weight, on a bike ridden at an angle briefly, it’s going to twist. If it’s happening when the pads are a long way off the rim that’s unusual but the effect itself is normal to some extent.

Well… I would accept that but I didn’t have the issue on my CAAD9 (which is why I was asking about frame flex, I could imagine the CAAD9 being less flexy than a Synapse). Also, when I am out of the saddle it’s not for big high geared efforts, its often just for ‘stretching my back out’ periods when I’m not putting a lot of stress through the frame i.e. I’m not tipping from side to side or hauling on the bars.

I guess I’m reassured it’s not the frame at least. Before I had any replies to this post I had already tightened the spokes 1/8th turn each, will be interesting to see what effect if any I notice. Will let the brakes out a bit more and see how it goes.

certain wheels can be quite flexible when side loaded i.e. going up a big climb standing up and moving side to side, and heavier or more aggressive riders will experience this more often?

my Fulcrum Racing 5s do this, I can get the back wheel to swish against the brake blocks on a steep climb, especially noticeable in the wet

Last week I borrowed an aero bike with full carbon wheels and was blown away by the speed on the flat, but could get the rear wheel to swish against the brake blocks by just wiggling my bum hard sat down in the saddle.

My handbuilts in contrast are rock solid with 32 spoke x 3 cross lacing and I have never been able to get any brake block contact out of those wheels no matter what I have tried!

i.e. I’m not tipping from side to side or hauling on the bars

Ok, more unusual then. Flex the rim sideways a bit with your fingers then try the same thing with a different wheel?

I’d thoroughly inspect the forks- pull them and check carefully. Steerer and each leg. I’d also borrow a front wheel from someone to ride/check. If your near me I’ve got a space wheel/tyre ready to go (Manchester).

FWIW, I test rode for a couple of hours a Carbon Synapse a couple of years ago straight after testing a SuperSix. My route went up Kirkstone pass and I found the Synapse to be err, comfortable? It flexed quite a bit more but then its designed to. It didn’t cause the blood to be shaken out of my hands on the descent like the Six did.

Thanks Hora, it’s the rear wheel I’m concerned about, not hit any corners fast enough to have issues with the front!

My boss runs some top of the range Mavic somethingorothers, will try and fit one of those, see what the difference is (and probably smash it through an unseen pothole or something 😕 )

I had this on a frame. Wheel swap didn’t do it, so changed frame as it was annoying me. Not a synapse though, it was an old alu frame for a steel winter frame. That fixed it.

If you put a bike in a turbo and when you’re giving it beans have a look down at the BB shell, it’s rather disturbing at first just how much they more around under pedaling loads.

Have you thought about backing the brake blocks away from the wheels a tad and seeing what happens then?

I’ve got a synapse carbon and never had an issue with the oem mavic wheels. I’m not heavy ( 11 stone) and am a spinner not a big power rider but have honked it out of saddle a few times and not had any flex. Youre welcome to come over and try mine if you want ( Barnsley or Wakefield)