Newbie question I have a specialized 29er. I have been riding a lot on the road and would like to get more top end speed. Can I change the chainring to a higher tooth count without changing the chain size and will that get me the top end sped I need to keep up to a road bike.

Chain length calculator

Adding a large chainring with more teeth might exceed the capacity of the front derailleur. Complete drivetrain info would help.

https://www.spinervals.com/products/item7.cfm

Oh. That's not what you were asking, huh?

sorry about that. I have a specialed rockhopper comp. disc 29
front der. shimano atlus 34.9mm, chaing ring 42 x 32 x 22, crankset shimano fc-m36108, cassette sram pg-830 11-32t Hope that helps.

no. I am looking to increase top end speed on my bike. mechanically

I think expecting to keep up with a road bike on a MTB is sort of unrealistic. They're just not made for that. If you made all the mods necessary to keep up with a road bike, you bike would be a road bike, just kind of a sucky one.

Two athletic dudes on expensive carbon road frames with biking jerseys were unloading their bikes from their car when I pedaled into the parking lot of a bike path on Sunday. By that point I was already on mile 25 of my 44 miler. They then proceeded to ride the entire 10 miles of the path at around 20mph, and I kept up the whole time on my MTB. They had to stop at the end to catch their breaths...

I kept going

Good for you, really, but the real roadies aren't toodling along at 20mph on the Amherst bike path. And it may be just me, but I find it very irritating when some random person latches onto my rear wheel and tries to get all competitive with me. If I don't feel like trying to drop them, I usually just slow down.

As it is, you have about 110 gear-inches, which is similar to a typical road bike in the 2nd or 3rd highest gear (53/13). You could probably change your big chainring to a 44 and end up similar to a road bike in one gear higher (53/12), but you will probably need a new chain and you need to verify that your derailleur has the capacity. Your LBS should be able to answer those questions pretty easily.

Of course, the same rider with the same gears has to work a lot harder to push a mountain bike tire than a road bike tire, so all else being equal, giving yourself another gear is not going to let you keep up with a road bike, unless the road cyclist is doing a lot less work than you are.

Thank You for the information, it is exactly what was I was looking for. Even though a newbie I ride 100 miles a week. A long ride on the weekend and short 10 mile sprints during the week. While new to the sport, I do know that a road bike is designed more for speed then a mountain bike. 700 tires versus 2.0 tires alone is a big deal. I ride on a combination of roads, bike paths, dirt and gravel during my travels. A road bike would not work for me. I don't want to commit to just roads either. I though more people would feel the same way but I am getting the feeling you must either be a dedicated road bike person or dedicated mountain bike person. I don't want to buy two bikes. Thanks.

There's nothing wrong with riding a mountain bike on the road. You get to the same destination, and you get the same, or more, fitness benefit as on a road bike. You just won't go as fast.

I bet that you have 2 bikes by the end of the year, though.

Sounds like you need a cyclocross bike.

I have those same gears and have done a few MTB races that have long road leadouts (1-2 miles). I can hit 25mph+ with those gears but not for a sustained ride. The gears are not your problem. I would guess it is your cadence.

The big problem will be in the rolling resistance of the tires and the wind resistance from the frame and position it puts you in.

You can put money switching those things around but then you get a bike that will do both trails and road but will do neither very well. Your best bet is two bikes or find what you like best and have the bike built for that and just deal with the other aspect with what you have.

Bingo.