carbon fork

[john evans]

hello fellow acc members i am after some advice from fellow members about carbon forks I acquired
i have fitted the carbon/alloy forks as you would normally but have uncounted a problem that it has dropped the frame by 12mm ie the bearing race has a lower distance to axel on the new forks than the standard fitted forks new 372mm and the old 384 mm will this affect the handling or cause problem i.e undue stress on the head tube also the wheel base has decreased by 2 mm. i would appreciate any advice thanks john

[Andrew G]

It's wrong. It should fit snug and correctly with no movement (other than rotational obviously) or you will have incorrect rake, geometry, handling, just about everything, as well as probably damaging the frame.

Do you have an internal or external headset, 12mm sounds like headset sized gap. Could it be that you have the wrong headset?

[john evans]

thanks for reply i think you have missread my problem all the headset is fitted correctly the problem is the crown bearing race to Axel distance (in the front fork)is less thus lowering the front of the bike by 12mm changing the head angle/lowering the bb also thanks

[john evans]

[quote="john evans"]thanks for reply i think you have missread my problem all the headset is fitted correctly the problem is the crown bearing race to Axel distance (in the front fork)is less thus lowering the front of the bike by 12mm changing the head angle/lowering the bb also thanks

[Andrew G]

Okay I'll admit I'm confused .

If the wheelbase has shortened and the distance from hub to headset has shortened then that would have made me think that the old fork was a (more) curved one, like an old steel one that placed the front wheel further forward. That would mean a straighter (new carbon) fork has a steeper rake and hence shortened the wheelbase. This will alter the geometry and handling, although maybe for the better. Old curver forks tended to give a more twitchy front end that the more current straighter fork which gives a more stable and direct front end. Too steeper angle though and it would go the other way with you being too far over the front wheel.

Mentioning an integrated headset makes me think that it's not an old steel frame though, but some aluminium frames came with aluminium forks which were more curved than carbon ones. My Dad's bike (before I gave him my old frame) for example came with an alu fork, he changed this to a carbon one later and did comment on improved handling.

An easy check is to hold the old fork alongside the new one and match at the headset and see if it's an increased curve/rake over the new one. If the old fork has a bit more of a curve and the wheelbase has only been shortened by 2mm than my guess without seeing it would be as I mention above and the handling will probably be improved and a bit more stable at the front. To give a simple check ride no handed and see if it feels more stable than no handed before.

All that said it shouldn't lower the front end at all. You didn't take a space out from under the stem at the same time did you .

[Andrew G]

Just thought, was the old fork one with bigger clearances for mudguards and the new one a tight clearance fork? Obviously having bigger clearances would need a bigger distance to the hub.

[john evans]

hi agn Andrew correct the old fork was steel and did have m g clearance it is a 2011 carrera tdf large (cheap) hence the fork change just a starter bike but carbon next year i have been checking angles and the h tube now 72/3 degrees to parallel better i believe bottom bracket 70mm down from wheel base that is now 100mm better i belive also so all looking towards positive change plus 650 grams lighter basicaly the gap between the brake caliper bolt fixing location and the bearing race is 12 mm less than original hence changes frame angles cause head tube is now sitting lower just wanted to cheack that his will not stress ht to much thanks john

[john evans]

[quote="john evans"]hi agn Andrew correct the old fork was steel and did have m g clearance it is a 2011 carrera tdf large (cheap) hence the fork change just a starter bike but carbon next year i have been checking angles and the h tube now 72/3 degrees to parallel better i believe bottom bracket 70mm down from wheel base that is now 100mm better i belive also so all looking towards positive change plus 650 grams lighter basicaly the gap between the brake caliper bolt fixing location and the bearing race is 12 mm less than original hence changes frame angles cause head tube is now sitting lower just wanted to cheack that his will not stress ht to much thanks john

[Andrew G]

Phew got there in the end! .
72 is a good head angle.

[john evans]

execellent thanks andrew always good to get second opinion i just got a bit of toe overlap to get used to now but only couple of mm so should be fine