Back ache - changing stem length?

[deanbmx]

After building my planet x up and it having a toptube length 20mm longer than my cube I have been getting back ache around the middle of my back. I think it could be a combo of too much stretch and maybe a little too much drop.

The stem is a 90mm 8° which is flipped pointing down (well level really) any suggestions other than flipping the stem?

 

[DooDah]

Saddle further forward?

 

[mattobrien]

Was the Cube too small for you or just right - just wanted to understand the reasons for going a size up - or did you go the 'same size' and it turned out not to be?

90mm stem is fairly short, so I am not sure how feasible it would be to lose the 20mm with a shorter one.

it may be a case of waiting for your body to adapt to the new riding position on the Planet X, I'd give it a little while longer before swapping things around.

 

[deanbmx]

The cube felt pretty good to be honest. Ive covered around 150 miles on the planet x. I may try shifting the seat forward a little first. Other thought is wether a 6° stem would make much difference?

 

[youngoldbloke]

Have you got the same bars and shifters on the PX?

 

[djb1971]

Flip the stem, add a spacer or two, as well as height this will reduce the length by a few mm. Check the setback on the seatpost, rotate bars backwards slightly, move saddle forward.

As already said, you may just need time to adjust to extra but 20mm is a lot of extra top tube.

 

[deanbmx]

Flip the stem, add a spacer or two, as well as height this will reduce the length by a few mm. Check the setback on the seatpost, rotate bars backwards slightly, move saddle forward.

As already said, you may just need time to adjust to extra but 20mm is a lot of extra top tube.

Im running as many spacers as I can. The previous owner chopped the steerer pretty short.

New bars but same shifters, bar measurements were pretty much the same as my old easton bars.

I will try shifting the seat forward first and see if that helps much. Small changes are the best way I guess.

 

[deanbmx]

Ive just remeasured the frame against the cubes specs and it actually isnt 20mm longer. Its more like 12mm and ive moved the seat forward around 15mm so hopefully that will work.

 

[amaferanga]

The saddle position should be set relative to the bottom bracket. Don't move the saddle forward to modify reach.

 

[Moodyman]

The saddle position should be set relative to the bottom bracket. Don't move the saddle forward to modify reach.

Indeed, moving the saddle can introduce other issues like knee pain

 

[mr messy]

80mm stem

 

[tigger]

Do you still have the Cube? If so it's easy to take the key measurements with a tape measure, plum line and spirit level and then transfer them to the Planet X (assuming size and geometry are similar). As the OPs have said, simply moving your saddle to compensate reach is terrible advice which I've seen too often on forums and even in bike shops! Saddle fore aft is relative to your saddle height and bottom bracket to help achieve the correct knee bend...

Measure the length from centre of BB to top of saddle at an angle straight along the seat tube.I'm assuming cranks are the same length, if not then adjust. Then using a plum line from the very tip of your saddle measure the set back from the line to centre of BB. Next is tip of saddle to centre of stem as a horizontal plain (long spirit level is good for this). Then measure the drop from spirit level to top of bars where the stem joins. That should get you pretty close.

 

[DooDah]

As the OPs have said, simply moving your saddle to compensate reach is terrible advice which I've seen too often on forums and even in bike shops! Saddle fore aft is relative to your saddle height and bottom bracket to help achieve the correct knee bend...

When I suggested moving the saddle forward, it was assuming (as the OP said) the geometry was similar and that he had not yet set up the bike. His knee may well be behind the axle of the pedal.