The Cantrell Motorsports Lap Timer is the app for the race track enthusiast seeking to improve via learning and sharing.

This is the easiest to use GPS-based lap timer, data recorder, video recorder, and performance analysis app available for iOS devices.

The app does not require any track information to function fully right out of the box. Simply mount it in your vehicle and the app uses GPS to automatically learn the track and pick a suitable start/finish location, which can be change later if desired.

This Pro version includes all of the free version's in-app purchase options at a reduced price.

Main Features

• No setup or calibration is required! Just mount and go!
• Automatic data and video recording; simply open the app to the Recorder screen and go!
• HD Video on devices that support it
• Synchronized data across all devices
• GoPro action camera auto on/of and auto record
• Real-time display of speed, g forces, OBD2 data, and lap times
• Immediate analysis of performance data and video at the track
• Lap and segment times
• Horsepower graph
• Automatic track mapping; no need for predefined track info
• High resolution GPS (upto 20Hz) using an external GPS module
• OBD2 data recording (using optional OBD2 modules such as the GoPoint BT1)
• Designed for auto-crossing, road racing, drag racing, karting, motorcycle racing, bicycle racing and more...
 • Data sharing via Bluetooth (device to device at the track!), e-mail, AirDrop
 • Share and compare lap times using the CMS Cloud Service
 • Export CSV files for use with apps such as TrackAttack and RaceRender

Overview of Operation

Recorded data is saved as Runs. Each Run starts when the vehicle exceeds 20MPH/33KPH and ends when the vehicle is moving slowly. The run includes several seconds of data before the recording trigger speed is reached. This way the start of an auto-cross run is included.

External GPS Modules

Due to limitations of the built-in GPS module, the data may suffer from inaccuracy. An external GPS module is recommended for improved accuracy.

Continued use of GPS running in the background can dramatically decrease battery life. Use of a power adaptor is highly recommended.

• Refer to the user guide for additional information:

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What’s New

Version 2.22

+ Rename location support
+ Auto-scale OBD throttle
+ App store review support
+ Help buttons for social media accounts
+ Draw segment beacon lines
+ Bigger fonts for graph values

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Ratings and Reviews

3.7 out of 5
3 Ratings

3 Ratings

SpeediCat ,

Works very well

I used this app at the recent track day. Having the in-app help section is very useful to learn how to use the app without having to run to the Internet. The app works very well and gives an accurate lap time. Occasionally, it fails to record at the start finish beacon and gives you a combined time for two or more laps. Support from the developer is top-notch. He was able to correct a bug in the application within 24 hours. The ability to place multiple beacons anywhere on the track map is invaluable.

tane39 ,

Simple on the track, powerful analysis at home

I used to use HLT but moved to CMS and have been very happy for the switch. I set up my iPhone behind me to record my hands and the road. So I don’t look at any data live. While I am at the track it starts and stops on its own (picking up my OBD and GPS unit). In between sessions I just skim lap times. Very easy. Once home, I use the analysis tool to see where I am doing well and doing poorly, and if what I was working on helped or not. This is where CMS really shines. I find my phone too small to look at data, so I grab my iPad and everything is there – syncing seamlessly and invisible through iCloud. I use “Layout 1”. I usually start by comparing the best lap of the day with my best lap ever. Up top are a track map and g-force circle. Then three charts for customizable data. I look at speed and throttle in the top box, LatG in the middle, and then “Time Slip” in the third (I don’t have brake data). Time slip shows the cumulative difference in time between the two laps. I find it really helpful to see the changes in relative performance between runs. Video is excellent learning (and sharing) tool too. Easy to export one or several laps. Data at the bottom is again track map, g-force circle, and 3 custom items (I use mph, LatG and Throttle). I find it useful to step through this video slowly (just tap the button). I like to see exactly where I am on the track and what the data looks like at that point. There is a lot of real estate at the bottom of the iPad and an enhancement I would like to see is minimum corner speed and maximum straight speed (like HLT).

Other enhancements I would like are maybe a way to group/organize the runs. I go to the track a fair bit, so I have a lot of runs (sessions). It would be nice to have them aggregate into days, or even months or years. Nice little feature of CMS here is that for each run it lists the best lap time, so you can see your progress at a glance.

I would also like if the track maps came pre-set with “segments”. I think you might be able to do this on your own by adding “beacons”, but I think if there was a preset beacon at the end of the brake zone after each major straight that would be a natural way of sub-dividing the track for analysis. You could then generate a “virtual best” over a series of laps (run, day, month, year) which would be a great learning tool.

KeithJOlsen ,

Awesome App

I bought this app to use for auto-x and hill-climbs. It works great! I've only been able to use it for auto-x so far but it is very accurate and give's you all of the information you could ever want about your run. It will tell your speed at any point on the course and G-forces. You have to buy an external GPS receiver to cover for the inadequacies of the phone, but that's a small price to pay to turn your iPhone into a $1000 data logger. It will also auto start/stop the video so you don't have to worry about missing your best run.
Also the developer responds to feedback and emails quickly. You can tell he is very interested in making this the most thorough data logging app possible on the iPhone. I highly recommend this app.


Pete Stoppani Consulting
18.5 MB

Requires iOS 9.3 or later. Compatible with iPhone, iPad, and iPod touch.



Age Rating
This app may use your location even when it isn't open, which can decrease battery life.


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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