Got a bit of a situation here, especially with weeks to go before a certain endurance based event.

This bike gets ridden 4ish times a week 80-100ish miles maybe, commuting, bombing about, errands – it fits me perfectly, and I love it.

This bike is my ‘proper’ bike.

I ride this once or twice a week for my proper MTB rides. Not had it long, only recently starting to use it on big days out.

This one, is starting to give me horrendous lower back pain after an hour.

Both bikes have the same –

BB-saddle height
Saddle-bar distance (effective reach)
Bar width
Chainset

Pretty much everything.

The only thing I can work out is that the effective seat tube angle on the Heckler is much, much slacker.

For the same reach, the Heckler is running a 50mm shorter, and a layback post, whereas the Kona has a straight post (a Thomson, not whats in the pic) and a 80mm stem.

So this, combined with the naturally slacker angles of the Heckler, means Im sitting much further back in relation the the front wheel (you can see this with both bikes lined up).

Or rather more importantly, further behind the crank. A lot further, maybe 50mm, maybe even more.

Is this it?

Is it stretching the back of my legs/lower back too much?

Whats the best solution – longer stem + straight post?

It probably is something to do with your Glutes as they are the cause of most lower back pain in cyclists – stretch them (and your hamstrings every day and see what sort of difference it makes.
Also go and get a Sports Massage – a proper one from a properly qualified therapist. I can tell you where to find one if you need

I had major backpain after a trip to spain earlier in the year it turned out to be a hamstring problem it kept me off my bike for quite a while 🙁

Duc – I’ve had that kind of advice from others, but i do stretch properly, and my Step mum is qualifed in that sort of thing

The issue is that I can ride the Kona like hell fire for hours, and theoretically it should be a less comfortable ride.

The Heckler – backbreaking in 45 minutes.

So I dont think its me, as such.

solution … ride the kona at mayhem ….there is absolutely nothing that needs a heckler at mayhem 😉

ps si .. you of all people should know you cant just whack a short stem on and use a layback seat post to compensate … all that happens is you lean over further when climbing to stop the front wheel rising …. where as on the kona you will be sat more upright due to the bike being ridden the way it was designed not like the hunch back of notredamn !

They have the same dimensions side by side, but not when you’re on them. The Heckler will sag at the back moving your weight and position on the saddle. This, coupled with the slack seat angle may be stretching you out in the cockpit. Also at that point your bars will be much higher than you’re used to on the Kona. Move your saddle forward and/or put a 20-30mm shorter stem and less stack height on the heckler.

I had similar, for a long time before I realized that it was the angle of the saddle that was forcing my lower back to be under constant strain.

Experiment with different saddle angles and it will become immediately obvious when you’ve sorted it.

Good luck

Just a suggestion, but compare measurements from one bike to the other when you’re sitting on one.
Also, check your fore-aft position over the pedals with a plumb line from your tibial tuberosity to the centre of hepedal spindle.

If your step mum is qualified then get her to do some work on you. Although that may feel a little weird 8O.
I still say that with all that its likely to be a problem related to tightness in your glutes and possibly hamstrings as well.
Incidentally I have no qualifications as such but am connected to quite a few qualified people.
The change in position relative to the bottom bracket will be making muscles work in very different ways. Is the Q factor the sane between the bikes?

Duc’s probably right. Check the relationship between your pelvis & low back – if you hold a broomstick from your sacrum (very bottom of back) up along your spine there should be a space over your low back before it touches further up. This should still be the case when you pedal, your pelvis shouldn’t move from side to side either.

Nose looks high on the santa cruz saddle.I had a lower back problem when I first went full sus. Turned out I was setting the saddle up when I was off the bike, forgetting the nose comes up with the sag on the rear shock, especally when your sitting pedaling up hill. Its now set so it looks angled down (a 5 degrees or so) when I’m off the bike, but is perfect when I’m on it pedaling. Worked for me.

Cheers guys.

– I cant ( and i definitely dont want to be!) putting a shorterstem on the heckler – its a 50!

– Saddles are now BG, set to same level in riding position. Seat angles dont change when in the riding position as my bike is setup correctly…

– Q factor is the same, as is crank length.

The effective top tube length, is the same on both bikes, and on the Kona its perfect.

The only difference is – that same top tube length is further behind the crank, on the Heckler. The Bar and Saddle are set back by an equal amount.

If I drop a line from my hip, on the Kona is passes through the chainstay at about the same point as the tyre – on the Heckler is about halfway along the chainstay.

Thus, I think its to do with the angle between my back, and my legs.
I’m over stretching the backs of my legs/backside.

I’m gonna get shim and stick the straight post in, and pinch a longer stem to try.

Take a little time out, you may be overdoing it, or stick to riding the non-achey bike as a process of elimination.

So what core muscle exercices are you doing? Yes the ride position will affect you – and there is a feel to when it is right (so much over hipped c**p about ride position). Cyclists all get back problems, but core muscles – they are your stomach muscles and pelvic floor, need to be strong enough otherwise your main back muscles fight to do a job they aren’t very good at.