Building up a bike from scratch, I have a MTB frame, it’s a Merida carbon race frame and need forks, I ride trails and some on road as well. What do you recommend, budget £150 for a good used set. And what size do I need?

Same size as the frame.

80 or 100mm would probably be what the frame’s designed for if it’s a race model but worth checking – some newer ones may be 120mm

RS Reba’s or SIDs or some Fox F100’s would be a reasonable choice.

getting something light and with some compression damping control or a lockout for road riding.

you need to work out stack height of headset+ stem+ headtube + a few spacers if buying second hand to make sure the fork will fit the frame.

RS Reba’s or SIDs or some Fox F100’s* would be a reasonable choice.

getting something light and with some compression damping control or a lockout for road riding.

+1 Reba and (new) SID’s can be had from the classified for that amount of mone.

*Purely a personnal choice, I just wouldn’t waste my money on em.

Forgot to say I will be using XTR V-Brakes on bike so forks need to accomodate those. Must admit I am confused by the sizes and what they mean. How do I know wether to get 80, 100, or 120mm? Should I base this on the size of the frame headtube?

XTR V-Brake?

Errr older Reba’s then… (not sure new SID came with V mounts and newer Reba’s definitely don’t)

How do I know wether to get 80, 100, or 120mm?

Look at the manufacturers website, as to what it orignally came fitted with. Though you usually can get away with 80-120mm on a short travel (XC) frame, unless it has very steep angle.

Should I base this on the size of the frame headtube?

Nope, but this, your headset, stem & spacers will make up the minimum steerer length on the fork you’ll need to buy.

youll want to stick to 100mm on that frame (ive got one)

its too steep with 80mm and its too slack with 120.

does the frame have V brake mounts …. mine doesnt !

I’d say something like a Reba Team with V-brake bosses

Yes my frame has v-brake mounts, when does your frame date from trail rat?