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If I change to a 160mm fork from a 150mm fork will it mess with the geo on my bike?

There’s so many variables with suspension that can change this anyway. A +10 mm fork running more sag could feel less slack then the stock fork running stiffer. I ran +30mm with a ton of sag on my hardtail and the geo felt totally normal.

i think it changes your head tube angle by .5 degrees, and it will lower your bottom bracket a bit. so slightly slower turning, a little more stable at speed. there are websites that you can calculate bike geometry (you input all your current values and then select what fork you want to change to) and it will spit out some numbers. usually bikes can be safely overforked 10-20mm (i emailed Santa Cruz to ask them about overforking and warranty, and they told me i was cleared to do +10mm). You can assess the geometry change but if you don’t already have a really slack HTA, your bike will likely just fall into the range of what bikes are coming with these days. you’ll be a little more prone to pedal strikes though with the lower bottom bracket. but if you’re fine with the slight geo changes, i say do it.

edit: i was remembering wrong. bottom bracket raises slightly.

10mm is perfectly fine. Plus or minus 20mm is the max usually recommended, after that, it changes the geo too much. Though i’m running my hardtail with +40mm travel, and she absolutely rips, so take that for what you will.

But if i were smarter, i’d stay with the 20mm rule.

I reached out to Norco about up forking my hard tail. They told me I was good at 10mm but 20 or more would negatively affect my geo. I went 20 anyways, for….reasons. 2021 fluid HT2, put on a rock shock 35 silver 140mm

I’ve stacked an additional 57mm onto the front of mine and am not looking back! (But it’s a potato from 2004.)

Same had a 2018 roscoe that came std with 120, then put a 160 fox 34 on it. Shit was mental just too good idk why they just don’t come out of the factory like that?

Right? Everyone talking about all the shit it’ll change and what to expect… and I’m sitting here wondering how the hell people are noticing such a tiny change. I guess this sub is way more in-tune with their ride feel than I am.

I just answered basically the same question in another sub, but for 20mm. I’ll just copy and paste the same info here… hopefully you’ll find it useful:

I’ve messed around with geo, mulleting, adding angle-sets and over-forking… quite a bit over the years. My current 2022 bike is overforked by 10mm and has a negative 1 degree angle set. My wife’s bike has a negative 2 degree angle set and my son’s bike if overforked by 20mm and has a negative 1.5 degree angle set.

It can do some great things for a bike… but it can also make them feel weird if you don’t understand what you’re doing, aren’t careful or go to far. Some things to think about.

1. Adding 20mm in travel will increase your axle to crown (which is the measurement you need to keep an eye on) by 20mm of course. However, forks don’t all have the same axle to crown measurements for a given amount of travel. For instance even switching brands with the same travel fork can change your axle to crown by as much as 10mm. I think a Rockshox Lyrik 160mm is 7mm taller than a Fox 36 at 160mm. So you need to find your fork’s axle to crown measurement and compare it to the fork you’re looking at. You could be increasing this measurement by 20mm, or it could actually be 30mm or even just 10mm, or anywhere in-between.

2. Every 10mm added to your axle to crown measurement adds 10mm to your stack height. Bikes are designed with specific head tube lengths based on the axle to crown measurements they plan on using to get a bike into a certain stack height. If you have your cockpit setup where you like it, including your stack height. You may need to remove or add spacers under your stem to get back to what you like. I say add because a fork with more travel will also sag a little more, so your static stack height may be a little different, especially if, like I mentioned above, the true axle to crown height change is less than the travel change.

3. Every 10mm added to your axle to crown measurement typically slacks your head angle approx. 0.5 degrees. So a 20mm increase will slacken by approx. 1 degree (a 65.5 degree HA will now be 64.5).

4. The same is true of the Seat Tube Angle… it typically slacks out by 0.5 degrees per 10mm. So a 76 degree STA will now be 75.

5. Adding 20mm will also increase your bottom bracket height by approx. 7mm, leading to a slightly higher centre of gravity. If you get a lot of pedal strikes, this can help with that slightly.

6. Reach is also affected… as you bike slackens, your handlebars move towards you, lessening your affective reach. For every 10mm added, your reach decreases by 5mm. So a 760 reach will now feel like a 750 reach. You can compensate for this by using a longer stem to get your reach back. But if you end up taking spacers away from under your stem, every 10mm taken away here will bring your reach back by 5mm.

That’s pretty much about it. If you ever want to dig deeper into the world of geo adjustments there are a couple good online calculators I use.

For simple ones, this works well – https://bikegeo.muha.cc/

And for more info and deeper dive, I use this one – https://madscientistmtb.com/bike-geometry-compare/

10mm is not a big change. It will make the bike a bit slacker and slower to turn in. But should not have any major handling issues.

If you are going to swap out the fork entirely make sure you check the axle to crown distance. When I wanted to go from 150 to 160 on my V2 Bronson I was worried about altering the geometry. However, the Bronson was engineeered at the time to use the RockShox Pike 150, and I was intending to use a Fox 36. As it turns out the Axle-to-Crown for the Pike 150 was virtually identical to the Fox 36 160, and due to that the geometry didn’t have a significant change, albeit once the fork compressed I’m sure a more comlicated ateration of geometry occurred due to compounding angles and other math-things.

I don’t know if RS and Fox still retain that difference, but finding a 160 with a similar axle to crown measurement would be in your best interest in my opinion.

Not sure what rockshox fork you have but you can swap the airspring with the C1 Debonair Upgrade Kit.

A much cheaper route to achieve the same goal. I did this with my Revelation fork to get 150mm and havent had any problems.

It’s just the recon. Not worth it to me with the 32mm stanchions. I want something a little more tough with some more travel

Aren’t these 140 from the factory?

Nevermind, this is the 27.5 wheels. You would be fine at 160.

Yes. It will raise up your front end a bit. It will feel like it turns a bit slower, and maybe a bit more stable at speed.

I have this bike.

I’ve ridden recons, Judy’s, Reba’s, pike, and fox 34 and the recon is by far my least favorite

If you’re upgrading that fork, you’re in for a good time 🙂

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