Is your 29er rigid fork suspension adjusted? If so I think it may raise the front “too much”.
If you had a frame that is designed to have 100mm suspension, you’d need a rigid fork that was suspension adjusted, to have the same(ish?) axle to crown distance as a 100 mm suspension fork provides.
All depends how much longer the 29er rigid fork is than your current fork.
There is no set size for a rigid fork so a fork for a 29″ wheel could vary by around 40mm. If you had a particularly long 29″ fork it would change your frame angles and also raise the front up too much while also giving your bike a bit of a chopper look.
bear in mind you want to look at the ‘sagged’ values of the suspension fork you’re replacing – this can be significant even if you’re using a fork designed for the wheel size of the frame, more so with a 29er fork in a 26″ frame.
Yup, that’s exactly what I did with my Exotics- I got them for a Soul so I wanted “long travel” rigids basically not the usual 100mm corrected ones. Basically buy on actual dimensions not on what it says on the listing.
It’d be going on a 456… the a2c is 470mm… my ‘maths’ tells me that’d be fine, & the equivalent of a 130mm 26″ fork sat in its sag…. a bit like northwind above.
Dunno if this helps, but both of my 26″ frames have 29″ forks and 26″ wheels (f&r) and they ride (subjectively) really well.
You’ll notice that I like to challenge the conventions of the bike-photo genre, by playfully flirting with unconventional ideas around things like logo/valve/crank alignment, and clear backgrounds, lending each picture what I like to think of as an earthy, rustic quality, befitting of racked, rigid steel bikes in countryside scenes, oft single-speeding, but all built up organically for a purpose, not just bought off the shelf.
It’s not always clear what makes a fork a 29er fork. The important thing is that its axle to crown height is within the limit of the frame’s design. I checked with Pipedream, the manufacturers of my frame, who advised that anything from 440mm – 480mm would work (the frame will take 90mm-130mm sus. forks). I was going to buy a 440mm fork but MRP, the manufacturers, recommended their 465mm length fork knowing that the frame as 26″ wheeled and could take up to a 130mm sus. fork; I bought as recommended, and rides really nicely.
MRP do a range of rigid forks (420mm up to 490mm, all I think with the same rake) and don’t seem to spec. them for specific wheel sizes. I’ve seen the 465mm fork I have sold as a 29er, 27.5er and (when one retailer was just selling the 465mm and 490mm) as a 26er fork. Fork heights and sag recommendations vary between suspension brands, but I’d guess that 465mm is roughly a sagged 110/120mm 26″ fork (450mm is usually suggested to be the equivalent of a 100mm fork).