Bike comfort / suspension seat posts

I've recently got a new CX bike (Merida CX 500) and have been having some comfort issues (sore butt & back) so am considering getting a suspension seatpost and wondered if anyone has used one before.

The CX is fine for shortish (20 mile) off-road rides, but I used it on Sunday for the 50 mile club run (with road tyres) and am now in pain. The bike setup (saddle height, reach and saddle-bar drop) is identical to my normal road bike, but the ride is rather harsher - primarily because the road bike is carbon whereas the CX is ally. I'm currently running 25mm GP 4000 tyres on the road at 90psi and was considering increasing to 28mm at slightly lower pressure. Although that should help, I doubt it will be enough.

I was researching other solutions and came across suspension seatposts. In particular, the Cane Creek Thudbuster (link below) seems to get really good reviews. It's a little odd looking and a bit heavy, but if it keeps me away from the chiropractor it would be worth it.

Has anyone used a Thudbuster or something similar?

Mike

www.wiggle.co.uk/cane-creek-thudbuster-s...7cprd%7c5360097892uk

Hi Mike,

I also run a CX bike as a winter bike.

Realise that you have said it is the same reach, stack etc but I would challenge you to re-test all this and experiment with it. The reason I say this is because the geometry is totally different between a CX and road bike, top tube length and significantly higher BB. This has a BIG impact on the set up and like you I suffered to begin with on the longer rides. I found I needed a much shorter stem and the saddle coming back more. After doing this the bike feels much better and also hasn't lost anything when ridden off road.

I doubt the cause is the material of the frame as most riders will say alu/steel is more forgiving than carbon. Carbon is much stiffer.

I too run my cx bike as a winter bike and once set up in line with Davids thoughts it is as comfortable as my road bike. My cx frame is also a carbon frame.

Before you start spending money on the seat post I would:

Change over the saddle from your road bike
Make subtle changes to the set up.
put some 28mm tyres on. I run GP4000s on the road at between 70-80psi

There's fundamentally no reason, once set up correctly why the cx bike should be any more uncomfortable than the road bike.

Gary

Dave / Gary,

Thanks for your comments. I'm pretty sure that the CX setup is the same as the road bike, but I'll check again.

One of the main reasons for buying the CX model I selected was because I could mimic the setup from the road bike (which took me a long time to fine tune). The top tube length is the same on both (as both are Merida 56cm frames). The road bike is a sportive bike (Merida Ride) so has a long head tube. I flipped the stem on the CX to get the same drop. I can't really see what else to change.

The reason I'm thinking of getting a suspension seatpost is mainly because of the CX reviews. Of the two reviews I read (Road.cc & BikeRadar), both said it was a great bike but "not the most comfortable" due to a stiff rear triangle. Dave, I know that carbon is stiffer, but my understanding was that carbon bikes are usually more comfortable as carbon can be made to be stiff where it's needed and compliant elsewhere (e.g. rear triangle) to absorb road buzz & aid comfort. Though I'm happy to be corrected on that.

Maybe I'll try switching the saddle and 28mm tyres first, as per Gary's suggestion.

Mike

Why not have a word with Martin Kirby (Club Member) who sells Merida.

I've taken on board the comments by switching my saddle and changing to 28mm rubber - comfort is now much better but I still have a problem with pace.

On the medium club run last Sunday (a pace I'm normally quite comfortable with) I struggled badly: being dropped whenever the pace quickened or we came to an incline. Now, I appreciate the CX bike is a couple of kilos heavier than my road bike (just over 10kg compared to just over 8kg), but I was wondering how much a wheel upgrade might help me. The standard wheels on the CX are unbranded Merida hoopswith Alex rims at I'd guess a little over 2kg the pair. I've been looking at the Kinesis Crosslight wheels, which get really good reviews and come in around 1.5kg at not too bad a price (£240). 0.5kg sounds like quite a significant weight saving that I should notice in pace improvement unless the weight of the frame is the nominant factor. Does anyone have any comment on this and the Kinesis Crosslights specifically?

I've discussed my issues with a few people and a couple have said "it's not the wheels, it's the gearing". Can anyone explain this to me, as despite being an A-grade maths student at school, I don't understand the logic. Most roadbikes come with a 30/34T chainset whereas the CX has a 46/36T setup. Both have an 11-28 cassette. Surely, the only important thing is the ratio of teeth on the front and back cogs? I understand that a 50/11 combination on the roadbike will give me a higher top speed than the 46/11 on the CX, but I'm not too bothered about top speed. For "normal" cruising, 50/14 on the roadbike gives a ratio of 3.57, so for every pedal revolution, the back wheel will rotate 3.57 times, whereas a 46/13 combination on the CX gives a near identical ratio of 3.54. Surely it doesn't matter how many teeth I have on the chainrings as long as I select an appropriate sprocket on the back? Please explain in a manner that my 48 year old brain can comprehend.

If someone can convince me that changing the chainrings to a 50/34T setup would solve my problem, I should be able to do that for ~ £50.

Basically, I can see 3 options:

1. Wheel upgrade (~ £240);
2. Change to 50/34T chainrings (~ £50);
3. EPO.

Thanks in advance for any feedback.

It's all beyond me, have you thought about option 4 yet?

Get another New Bike (joke).

That's precisely why I've having this bother, Mark!

I think you need to honestly consider a 4th option.

4. Suck in the extra effort the CX bike gives you as winter training It will make you fitter in the longer term and faster when you get back on your summer stead.

A CX bike is designed for offroad, thick mud, carrying and tight corners. The genetic makeup of the frame is different, you need to transfer more of your weight to the rear of frame to increase traction. I know you have tried to match it to your summer road bike but it would be step too far to expect it to perform in the same way. It was always going to be a bit slower from a performance perspective.

Don't spend anymore money and just keep riding it as you will get faster

David - what are you saying - no more excuses to buy new kit!!!

Seriously though, you're probably right.

how many miles do you ride in a week on average ?? Geoff,,

Clearly not enough, Geoff.

I did 4,000 miles last year, which works out at 100+ per week in the summer and 50 or so per week in the winter. I'd like to do more, but that's more or less my realistic limit without compromising family & work commitments.