![]() ![]() It’s something to consider when dialing in your new setup if you find front wheel traction issues. Read more on Wheel Flop on Wikipedia HereĪlso it’s important to remember in a world of 2.5mm stem spacers and 5mm stem lengths when you mullet that 27.5″ your hands are going up and back. I think I would feel the 7.7% difference in trail but more notably the nearly 11% change in wheel flop during steering input. I’ve gone down this rabbit hole previously comparing the 160 and 150mm fork options on the SB130 – but again I come back to trail and wheel flop. I’d also go on a limb and say I’d be hardpressed to feel a sub 2% change in a lot of things on my bike… So if it’s not the headtube change you’re feeling what is it? I would say most sport level riders would feel the difference between the 180mm stock and 170mm mullet bike. Let’s look at numbers we can compare (again don’t use these as Jeopardy answers but you get the point…) Sidenote: The modification to these dimensions from the fork height needs to have the headtube angle compensated for, but the radius gain is the same no matter what. Well this forces the front end up, pivoting on the rear wheel axis, increasing stack while decreasing reach. Then you add the radius difference between tire sizes, for this we’ve gone with a clean 27.5mm and 29″ diameter but they do vary a bit with tires, the less travel fork again adds 19mm. The fork with less travel, albeit bigger wheel, is 8mm taller axle to crown. Using Yeti’s geo charts we see the SB165 27.5″ 180mm is listed at 569.1mm axle to crown. So given the 29er has a larger radius it is typical for both geometry considerations as well as keeping the wheel off the downtube to go to a smaller travel option like the 170mm 29er versus the 180mm 27.5 on the SB165 mullet. If it can hit the frame it WILL stop the front wheel turning you into a lawn dart. You don’t compress a fork all the way going slow, in flats, where you can correct this. ![]() If at any time the tire can contact the frame you’re gonna get hurt. Remember that in full compression your tire will expand at the top (as the bottom of the tire is forcibly compressed). ![]() ALWAYS check that at full compression the front wheel has clearance of the downtube. Some considerations if you’re planning a mullet. ![]() I decided to build out a couple more options into the model to help highlight where all the changes are. So why does less than 2% difference and less than 1 degree headtube angle feel like such a notable change? So the quick answer to the question: “What would be the head angle of the SB165 in mullet config with 170mm 29″ fork?” It’s about a degree slacker coming in just under 62.5 degrees. From that point we rotate the model on the rear wheel axis until the front wheel is raised to the appropriate height.Īlright. We build a model and then extend the axle and crown down and change the offset. In this case the model utilizes the stock size M SB165 wheelbase, an estimated wheel radius (27.5/2), the published axle to crown of 569.1 as well as the 63.5 degree headtube angle. So until BikeCo gets a grant to do it we use models to expedite this. All of these factors make it a bit complex (for me at least) to calculate the geometry and trig needed. When you’re working with a front wheel modification like the SB165 or SB140 your fork offset is also likely to change. Front wheel radius increases or rear wheel radius decreases depending on setup. With a mullet bike you’ve got other factors as well. Headtube angle, trail, flop, reach and stack are all modified when you increase or decrease axle to crown distance. So some riders will be familiar with the geo modifications from bikes like the SB130 or SB140 Lunch Ride setups. We’ll have some basic concept and comparison of how one change directly modifies a whole bunch of the handling. It could be a thesis trying to explain how these changes directly modify performance so we’re not going there today. Point is, these numbers will give you an idea of the concept I wouldn’t bet the farm on precision four points behind the decimal… These models aren’t gospel truth on geo, but having been in this game for a lot of years some of the geo’s you’ve seen published I wouldn’t take for gospel either. I couldn’t find Yeti’s published SB165 Mullet geo so I build a model to review. What started as a quick email reply of concept turned into a more thorough review and I thought with more questions on MTB mullets these days we could put it up on a post for everyone. How did the headtube angle compare between the Yeti SB165 in a 27.5″ stock setup with a 180mm fork compared to the Mullet 29″ 170mm concept? In particular headtube angles and performance. More MTB Mullets – Comparing Travel, Headtube, Trail & FlopĪn interesting question come across my email wondering about MTB Mullet setup. ![]()
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