zinncycles

This is getting fun. Thanks for all the great insight. Couple quick things: Zinn road and gravel bikes are custom, so you can get whatever bottom bracket height you want. We aren’t going to force anyone to use proportional cranks. It’s merely a recommendation. Full suspension bikes have some customization available too, but maybe a little less. So feel free to ask and we can see what we can do. We are definitely open to newer styles, and still feel there is a place for more compact bikes. The main thing I see is that every change to geometry is going to have some positive impact and some negative, and that impact will be different for different people depending on how they like to ride. From my experience, every single person that has ridden our bikes for the past 15 years has absolutely loved them. So, should we change it? Clearly there is a place for this style of geometry. It’s maneaverable and yet stable, but could certainly be more high speed stable for those that love to go really fast. Are we missing out on sales because our reach is not long enough, i guess that seems likely at this point. Perhaps our main customer base is old school and likes the “2012” geometry style, but we could open up to a new market if we modernized it more. So maybe we need a 2nd version of the bike that is long and slack and keep the current style one for those that prefer technical maneuvering. One cool thing about being a small company is we can play with designs on a one off basis and see how it goes. Do we also need to update the way the frame looks? Yeah probably. Keep an eye on us for 2026. I’d say it’s time for a new look. Feedback definitely noted and taken seriously. I do think it’s interesting the emphasis that frame reach has had on everyone’s perception of bike geometry. Here are the different things that affect frame reach. Top tube length. Obviously if you make the effective top tube longer without changing anything else, reach is increased along with wheel base. This also makes for a longer “seated reach” in addition to longer “riding reach” Steepen the seat angle. This seems to be what a lot of brands are doing. I’ve been looking around and I see a lot of 77-79 degree seat angles but with classic length top tubes. I’m very curious about this. Classically, people didn’t do this because it put the knee too far forward over the crank, but that seems to be a non issue any more. Thoughts? Steepening the seat angle gets more frame reach without changing seated reach. Shorten the fork: if you shorten the fork, this also increases reach, but also shortens wheel base. Decreasing stack by shortening the head tube increases reach without any affect on wheelbase. So our bike could have everything the same, but with a 4” head tube and our reach numbers would be significantly longer, but would this change anything about the way the bike handles? I doubt it would. People would simply add spacers which would effectively bring the “reach” number back to where it started. Steepening the head tube angle also has a small increase on reach while reducing the wheelbase. What affects wheelbase The things mentioned above Increasing or decreasing fork offset will have an affect on wheelbase. Longer chainstay What affects bike stability? Clearly, wheel base has an effect on high speed bike stability, but will have a negative effect on tight maneuvering, like switchbacks. This is what always gets us worried on big bikes. Making them so long that people feel like they can’t maneuver them. I would say this is the biggest reason we have avoided super long bikes. They are already so big, we didn’t want to make them so cumbersome for guys to handle. But it sounds like people end up getting used to it.. ? Fork trail. This is one if the biggest affects on how a bike handles. More fork trail means more high speed stability while also causing more wheel flop at slower speeds making it harder to maneuver in tight technical terrain. So you could have a bike with a crazy long wheel base that was still twitchy at high speeds if the fork trail was super low. The converse is also true. I don’t see many brands posting fork trail on their geo charts. I think I am going to start doing that. What have you guys found to be the ideal fork trail on the modern “longer reach” bikes? Here is an article Lennard wrote about bike stability and fork trail. He did his college physics senior project on bike stability back in1980 and has spent a lot of time studying and testing it throughout his career https://zinncycles.com/bike-stability-good-or-bad/ Center of gravity. If you raise the bottom bracket without increasing crank length, center of gravity goes up. If you raise the bottom bracket while increasing crank length the same amount, center of gravity remains the same. This is true while seated and while standing on the pedals. The bigger stance cancels out the increase in bb height. Similar to how a tall person would want to have a wider stance on a snowboard than a shorter person

also the center of gravity while seated also remains the same. since if you raise the bottom bracket and lengthen the cranks, the seat height from the ground will be the same. If a tall guy uses 175mm cranks, their seat height from BB will be 25mm taller than it would be with 200mm cranks.

sorry guys. 345mm is the unsagged BB height not 385 as originally posted. Sorry for the typo.

@nnowak: We have worked a lot with Lee McCormack and design bikes more around his Ridelogic style of fitting. https://leelikesbikes.com/i-cant-believe-im-a-size-xs-about-mountain-bike-sizing.html I know not everyone agrees with him either, but we do.

@bushbush111: please recommend someone. that would be greatly appreciated.

@nnowak: maybe you are right but this simply has not ever been the experience of anyone who actually rode one of these bikes. Maybe it's not optimal for everyone, but when people buy the bike and ride, they all love them. That tells me a lot.

but I will discuss with Lennard and see what he thinks about geometry.

I did a roll out measurement to get the circumference and calculated the diameter off of that at 808mm when mounted to Nextie Unicorn Carbon rims. but then the tires seem to expand after a few rides.

@nnowak: I'm going to need to double check this one. I may have that number wrong. You are right it's only supposed to be the equivalent of crank length. I'll update once I figure it out.